THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


(Sutbts  to  the  fgtn&mm  of  tlu  Boston  Sorittg  of  |tatural  Historg. 


GUIDE   TO    THE   INVERTEBRATES 

OF    THE 

SYNOPTIC  COLLECTION 

IN  THE  MUSEUM  OF  THE 
BOSTON  SOCIETY  OF  NATURAL  HISTORY. 

BY  J.  M.  ARMS  SHELDON. 


BOSTON  : 
PUBLISHED  BY  THE  SOCIETY. 

1905. 


^-Y1-  I  I 

BIAS 


TABLE   OF   CONTENTS. 

Introduction       .          .         .          .         .         .         <         .         .  3-8 

Arrangement  of  Synoptic  Collection      ....  9-12 

PROTOZOA     .         .         '.        .        .....  13-59 

Sarcodina  —  Monera          .        .        .         .         .         .  13-20 

Rhizopoda     .         .         .         .                 .  21-38 

Heliozoa        .                  .        .        .         .  39 

Radiolaria     ......  40-44 

Mastigophora 45-52 

Infusoria .         .         .  53-58 

"         Tentaculifera      ......  59 

MESOZOA        .........  60-62 

METAZOA 63-494 

PORIFERA         .            . .  63-88 

Calcarea      .         .         .         ..       .         .         .         ...  68-73 

Silicea          .         .         .         .         .         .         .         .         .  74-83 

"        Hexactinellida        .        .         .         ,         .         .  75-76 

"        Lithistidae     .         .         .        ...         ".  77 

"       Tetractinellida       .                  .         ...  77 

"        Monaxonia     .         .         .        .        ".        .         .  78-83 

Keratosa     . 84-86 

Summary         ........  87-88 

COELENTERA             .            .                        .            .            .            .            .  89-143 

Hydrozoa    .         .         ...         .         .         .         .  89—112 

Hvdrophora    ........  89-104 

Hydrocorallinae         ...       .         .  93~95 

Narcomedusae  .         .         .         .         .  96-97 

Tracomedusae   .         .         .         .         .  98 

Anthomedusae           .         .         .         .  99-100 

Hydroidea          .         .         .         .         .  101-103 

Campanulariae           .         .         .         .  104 

Discophora     . 105-108 

Siphonophora         .         .         .         .         .         .         .  109-110 

Ctenophora 111-112 

Aiithozoa    .'       .         .         .         .         .         .         .         .  113-141 

Alcyonaria       . 113-125 

Zoantharia      ........  126-130 

Madreporaria           .......  131-141 

Imperforata     .....  131-138 

Fungidae          .....  139 

Perforata           .....  140 

Summary     .         .         .         . ".    .         .         .         .  141-143 


ECHINODERMA          '            .            .            .            .            .            .            .  145-195 

Cystoidea 145-148 

Blastoidea           .         .         .              -  .         .        .         .  149-150 

Crinoidea .  151-160 

Asteroidea           .        . 161-168 

Ophiuroidea       .         .         .         .         *         .         .         .  169-170 

Echinoidea          .         .         .         .         .         .                  .  171-189 

Clypeastroids          .         ...         .         .         .  182-186 

Spatangoids    .         .         .         ...         .         .  187-189 

Holothuroidea    .         .         .         .       .*.'".         .  •:  190-192 

Summary 193-195 

MOLLUSCA      .        .         .         .        ....         .  196-263 

Pelecypoda          .         .         .         .         .  .     \         .         .  196-212 

Gastropoda          .         .         .         .         .         .         .         .  213-232 

Nudibranchs       ........  233-231; 

Scaphopoda 236 

Heteropoda         .         .        .        .        ,        ."        .         .  237 

Pteropoda  .         .         .         .         .         .         . '     '  ,"        .  238-242 

Cephalopoda       .         ...         .         .         .         .         .  243-261 

Tetrabranchiata      .......  244-256 

Nautiloidea          .         .         ..       .         .         .         .  244-249 

Ammonoidea       .         .         .   "      *         .         .         .  250-256 

Dibranchiata           .         .         .         .         ...         .  257-261 

Belemnitidae        . 257-261 

Summary '.  262-263 

VERMES          .         .         .         . 265-324 

Brachiopoda .  265-286 

Atremata          .         .         .         .         .         .         ,         .  265-269 

Neotremata     .         ,        ...         .        .        .  270-271 

Protremata      .         .         ...         .         .         .  272-275 

Telotremata    .         .         .         .        .        .         .         .  276-286 

Polyzoa       .         .         .         ...         .         .         .  287 

Annelida     .         .         .         .         .         ...         •         •  288-308 

Chaetoptera    .         .         .         .         .  .    ",.        .         .  288-304 

Oligochaeta 305-306 

Hirudinia        .         .         .         .         .         ,.        .         .  307-308 

Gephyrea    .         .         .         .....         .  309-310 

Nematodes          .                  .         .         .         .         .         .  311-313 

Acanthocephala          .'                  314 

Nemertea 315-316 

Turbellaria          .                  317-320 

Trematodes         ....                 ...  321-322 

Cestodes     ....         .        ...         .  323-324 

CRUSTACEA    ....        .        .        .        .        .        .  325—360 

Entomostraca     . 325~33o 

Cirripedia 33I~332 

Malacostraca 333~34O 


Macroura    .         .         .         .         .         .        .        ..        .  341-352 

Brachyura            .         .         .         ...         .         .  353-360 

ARACHNOZOA         .        .        .        .        .        .        .        .  361-377 

Trilobita -    ...        .         .  361-363 

Merostomata      .         .         .         .....         .  364-365 

Arachnida            .         .         ...         .         .         .  366-377 

MALACOPODA         .        ...        .        .        .        .  378-381 

MYRIAPODA   .        .        .        .        .        .        .        .        .  382-385 

SYMPHYLA     •        .        .                .        .        .        .        .  386-387 

LNSECTA          . 389-494 

Thysanura           .                  ,         .         .         .         .         .  389-395 

Ephemeroptera 396-399 

Odonata       .........  400—403 

Plecoptera .  404 

Platvptera 405-410 

Euplexoptera 411-412 

Orthoptera          .         .         .        .         .         .         .         .  413-417 

Thysanoptera     .         . 418 

Hemiptera           .         .         .         .         .         .                  .  419-431 

Coleoptera          .        .                 .        .         .         .         .  432-441; 

Neuroptera         .         .         .         .         .         .        .         .  446-448 

Mecoptera       ...         .                 .        .         .         .  449-450 

Trichoptera 451-453 

Lepidoptera        .        .         .        .         .         .         .         .  454-474 

Hymenoptera     .         .         .         .                  ...  475-486 

Diptera 487-494 


INTRODUCTION. 


IN  many  of  our  natural  history  museums  one  room  is 
devoted  to  a  Synoptic  Collection  of  animals.  The  stu- 
dent who  wishes  to  get  a  comprehensive  view  of  the 
whole  animal  kingdom  spends  most  of  his  time  on  such 
a  collection,  since  it  embraces  representative  forms  of 
all  the  principal  groups  from  the  simplest  protozoan  to 
the  most  complex  mammal;  in  other  words,  from  the  Pro- 
tamoeba  to  man  inclusive. 

It  may  be  truly  said  that  mankind  is  seeking  as  never 
before  for  a  rational  explanation  of  the  origin  and  the 
development  of  animal  life  upon  our  earth.  The  more 
strenuous  this  search,  the  more  imperative  is  the  demand 
made  upon  naturalists  to  present  in  their  museums,  so  far 
as  possible,  the  most  advanced  knowledge  concerning 
these  problems. 

At  the  present  time,  therefore,  it  is  not  enough  that 
a  Synoptic  Collection  consist  merely  of  specimens  of 
animals  effectively  or  artistically  arranged.  Neither  is  it 
sufficient  that  such  a  collection  consist  of  species  placed 
together  by  some  arbitrary  and  artificial  method. 

The  student  of  the  New  Zoology  demands  that  rela- 
tionship shall  be  the  basis  of  classification,  and  that  not 
only  the  descendants  living  to  day  shall  be  represented, 
but  also  their  primitive  ancestors  that  existed  in  an  early 
geologic  age.  Indeed,  a  genealogical  classification  of 
animals  is  the  goal  to  be  striven  for  constantly  by  the 
naturalist  of  the  twentieth  century.  The  recognition  of 
the  possibility  of  such  a  classification  tends  toward  the 
unification  of  collections  which  have  hitherto  remained 
isolated.  For  instance,  it  has  been  customary  to  place 


4  INTRODUCTION. 

together  all  ancient  animals  existing  in  the  form  of  fossils. 
These  have  been  arranged  stratigraphically,  beginning 
with  the  fossils  in  the  oldest  strata  and  ending  with  those 
in  the  newest,  or  vice  versa.  For  the  purpose  of  historic 
geological  study  or  for  strictly  palaeontological  research, 
such  collections  are  helpful.  This  arrangement  has  been, 
indeed,  the  only  one  possible  up  to  within  a  very  recent 
period.  Even  now  there  are  naturalists  who  seriously 
question  whether  any  other  method  of  arrangement  -"is 
possible.  These  maintain  that  our  knowledge  is  not  ade- 
quate to  warrant  an  attempt  at  a  natural  classification  of 
animals  based  upon  genetic  relationship. 

It  must  be  borne  in  mind,  however,  that  a  vast  amount 
of  material  in  the  form  of  well  proven  facts  has  accumu- 
lated since  1859,  when  Darwin's  Origin  of  Species  gave 
a  new  directive  impulse  to  biological  research.  This  ma- 
terial is  found  largely,  it  is  true,  in  an  almost  infinite 
number  of  papers  in  which  isolated  adult  species  are 
figured  and  described.  But  notwithstanding  this  fact,  it 
is  also  true  that  of  late  years  there  has  been  a  growing 
tendency  toward  considering  the  life  history  of  the  indi- 
vidual species  described,  and  this  study  has  led  in  turn 
to  an  investigation  into  the  life  history  of  the  group  to 
which  the  given  species  belonged.  In  this  way  the  signi- 
ficant correlation  sexisting  between  the  development  of 
the  individual,  known  as  ontogeny,  and  the  development 
of  its  class,  or  phylogeny,  have  been  discovered.  When 
it  is  remembered  that  these  correlations  are  proofs  of 
relationship  or  of  descent  from  a  common  ancestor,  then 
one  begins  to  realize  how  many  trustworthy  guides  there 
are,  all  pointing  toward  the  desired  goal.  Our  artificial 
classifications  of  animals,  therefore,  are  not  due  "  so 
much  to  insufficient  knowledge  of  their  early  stages  as 
to  insufficient  attention  to  what  is  actually  known  and 
published  regarding  them,"  as  Mr.  Samuel  H.  Scudder1 

!The  Butterflies  of  New  England,  I,  1889,  p.  viii. 


INTRODUCTION.  O 

has  already  pointed  out  in  the  case  of  the  arbitrary  clas- 
sifications of  the  Lepidoptera.  When  all  this  knowledge 
is  brought  together,  assorted,  and  systematically  used, 
then  the  sequence  of  life  upon  our  planet  will  be  demon- 
strated as  never  before.  Then  the  isolation  method  of 
arrangement  to  which  I  have  alluded  will  be  relegated 
to  the  past  and  students  will  no  longer  receive  the  lasting 
impression  that  fossil  forms  are  distinct  creations  having 
no  connection  with  living  organisms,  but  each  museum 
will  be  in  itself  a  revelation  of  the  essential  unity  of  all 
animal  life. 

It  is  true  that  many  of  our  museums  are  so  con- 
structed that  they  are  ill  adapted  for  the  demonstration 
of  the  evolution  of  inorganic  and  organic  nature.  But 
where  this  demonstration  cannot  be  given  with  complete- 
ness, minor  collections  like  a  Synoptic  Collection  of  geo- 
logical or  zoological  specimens  may  point  out  the  way  to 
the  desired  end. 

The  following  principles  of  classification  Professor 
Alpheus  Hyatt  wished  to  have  carried  out  in  the  Synop- 
tic Collection  of  this  Museum,  of  which  he  was  Curator 
during  the  preparation  of  nearly  all  of  this  Guide. 

First :  In  the  arrangement  of  the  material  proceed 
always  from  the  simple  to  the  complex. 

Second  :  So  far  as  possible  let  each  group  be  repre- 
sented first  by  its  primitive  ancestors  that  lived  in  the 
pre-Cambrian,  Cambrian,  or  early  Palaeozoic  times. 

Third  :  From  these  primitive  ancestors  pass  to  the 
embryonic  and  larval  stages  of  generalized  members  of 
the  group  existing  to-day  ;  and  from  these  early  stages  to 
the  adult  stages  which  are  invariably  more  specialized. 

Fourth  :  From  the  generalized  adult  members  in  every 
group  proceed  to  the  specialized  members  which  have 
reached  their  present  condition  through  the  law  of  spe- 
cialization by  addition. 

Fifth  :  In  some  of  the  most  impressive  instances  go  still 
farther  to  those  extremely  specialized  adults  which  have 
become  so  by  the  law  of  specialization  by  reduction. 


O  INTRODUCTION. 

We  have  attempted  to  carry  out  these  principles  in  the 
different  groups  of  invertebrates.  With  the  increase  of 
knowledge  certain  animals  which  are  here  described  as 
primitive  will  doubtless  be  found  to  be  reduced  forms, 
while  certain  reduced  forms  may  in  reality  be  primitive. 
Notwithstanding  these  changes  in  the  position  of  species, 
the  principles  of  this  genealogical  classification  will  remain 
essentially  the  same. 

In  order  to  bring  ou*  these  principles  clearly  and  for- 
cibly in  the  descriptive  text  of  the  Guide,  it  has  been  neces- 
sary to  abandon  altogether  the  use  of  certain  terms,  while 
the  meaning  of  other  terms  has  been  restricted.  Among 
those  given  up  are  the  words  "high,"  "low,"  "highest," 
"lowest."  Textbooks  and  manuals  have  usually  consid- 
ered animals  as  either  "high"  or  "low."  Generally 
speaking,  vertebrates  have  been  studied  first,  as  the 
"highest"  representatives  of  animal  life,  and  all  other 
forms  have  been  "low"  in  comparison.  In  other  cases 
the  study  of  a  class  has  begun  with  the  so  called  "  lowest" 
forms  ;  for  instance,  the  Crustacea  with  the  barnacles. 

These  classifications  were  the  best  that  were  possible  at 
the  time  they  were  made,  and  they  met  the  necessities  of 
the  period.  But  the  time  is  now  ripe,  as  we  have  already 
said,  for  a  more  natural  system  of  classification  which  shall 
embody  and  set  forth  the  history  of  animal  life  on  our 
globe.  In  a  genealogical  classification  that  illustrates  the 
broad  natural  relationships  which  bind  animals  together 
genetically  there  can  be  no  "  high "  nor  "  low."  There 
can  be  only  simple,  primary  forms  from  which  have  been 
evolved  in  the  process  of  the  ages  complex  and  secondary 
forms.  This,  in  reality,  is  the  fundamental  principle  of 
our  classification.  Granted  that  this  is  true,  then  the 
most  profound  knowledge  is  needed  concerning  the  prob- 
lems of  heredity  and  of  variation.  Immense  strides  have 
been  made  the  past  quarter  of  a  century,  and  epoch-mak- 
ing monographs  on  the  development  of  certain  animals 
have  thrown  strong  light  on  these  difficult  problems. 


INTRODUCTION.  7 

We  maintain  that  this  new  light  should  be  reflected  in 
our  museums,  especially  in  our  Synoptic  Collections  ;  that 
here  the  workings  of  the  law  of  heredity  by  which  ani- 
mals are  bound  together  by  blood  relationship  should  be 
illustrated  by  specimens,  drawings,  models,  by  everything 
in  brief,  that  can  most  strongly  impress  the  student.  This 
demonstration  would  be  more  effective  had  we  a  closer 
acquaintance  with  the  ancestral  fauna  of  pre-Cambrian  and 
Cambrian  times.  The  masterly  researches  of  Walcott  into 
the  Cambrian  and  Lower  Silurian  rocks,  and  the  invalu- 
able investigations  of  Matthews  in  the  Cambrian  forma- 
tions of  New  Brunswick  prove  how  important  are  these 
sources  for  studies  in  evolution  in  a  field  hitherto  almost 
unexplored. 

Other  terms  which  do  not  appear  in  this  Guide  are 
"degraded,"  "degenerate,"  "retrogressive,"  and  "worm" 
as  applied  to  the  caterpillar  stage  of  the  Lepidoptera. 

The  first  two,  "  degraded  "  and  "  degenerate,"  are  not 
used  for  two  reasons  :  first,  because  they  are  associated 
in  the  popular  mind  with  moral  considerations,  and  this 
association  often  leads  to  mental  confusion ;  secondly, 
because  we  cannot  see  why  an  animal  that  has  developed 
a  part  or  an  organ  to  the  immense  advantage  of  itself  and 
its  race  should  be  called  "degraded,"  even  though  many 
other  organs  have  fallen  into  disuse  or  wholly  disappeared 
in  the  process.  In  the  case  of  parasites  the  use  of  these 
terms  might  be  more  allowable,  were  it  not  for  the  first 
reason  stated. 

The  word  "  retrogressive"  is  not  used  because  it  is  mis- 
leading, since  animals  do  not  in  reality  go  back  to  a  more 
primitive  and  generalized  condition,  however  much  they 
may  appear  to  do  so.  This  is  proved  by  the  position  of 
the  so  called  "  retrogressive  species "  in  a  genealogical 
record  which  can  never  be  among  the  ancestral  trunk 
forms.  It  cannot  be,  because  these  species  as  a  rule  bear 
evidences  of  the  evolutionary  stages  through  which  they 
have  passed ;  and  where  such  evidences  are  not  apparent 


8  INTRODUCTION. 

to  the  eye,  it  is  rational  to  infer  that  vestigial  organs  can- 
not be  the  same  as  rudimentary  organs. 

The  use  of  the  word  "worm"  is  restricted  to  members  of 
the  subkingdom  of  Vermes.  It  is  obviously  misleading  to 
apply  it  to  such  a  specialized  animal  as  a  young  butterfly  or 
moth. 

"Simple"  and  "rudimentary"  are  used  only  in  describ- 
ing primitive  and  generalized  forms  or  organs. 

"Direct  development"  applies,  as  we  use  it,  to  the 
mode  of  development  of  the  more  generalized  members  of 
a  class.  Some  naturalists,  on  the  contrary,  use  it  in  the 
sense  in  which  we  have  used  accelerated  or  abbreviated 
development;  the  latter  we  apply  only  to  the  mode  of 
development  of  the  forms  specialized  by  addition  or  reduc- 
tion. 

Primitive  forms  are  spoken  of  as  primary,  generalized, 
simple,  fundamental ;  they  have  a  primitive  or  a  direct 
development,  and  some  of  their  organs  may  exist  as  rudi- 
ments, hence  the  adjective  rudimentary. 

Specialized  forms,  on  the  other  hand,  are  spoken  of  as 
secondary,  differentiated,  complex,  adaptive ;  their  devel- 
opment is  either  indirect  (with  a  metamorphosis),  accel- 
erated (where  the  early  stages  are  passed  through  quickly 
or  skipped),  or  suppressed  (where  the  advanced  stages 
are  omitted)  ;  some  of  their  organs  may  exist  as  vestiges, 
hence  the  adjective  vestigial. 

The  invertebrates  or  animals  without  a  vertebral  column 
are  divided  primarily  into  three  divisions,  the  Protozoa, 
Mesozoa,  and  Metazoa.  The  Protozoa  are  represented  in 
the  collection  by  many  forms,  the  Mesozoa  by  one  species. 
The  Metazoa  are  subdivided  into  nine  large  groups,  the 
Porifera,  Coelentera,  Echinoderma,  Mollusca,  Vermes, 
Crustacea,  Arachnozoa,  Myriopoda,  and  Insecta.  Some 
of  these  groups  are  again  divided,  as,  for  instance,  the 
Insecta,  where  typical  forms  of  sixteen  orders  are  figured 
and  described. 


THE    SYNOPTIC    COLLECTION. 


A  Synoptic  Collection  of  animals  possesses  one  advan- 
tage over  special  collections,  since  it  may  illustrate  on  broad 
and  general  lines  the  principles  of  a  natural  classification. 
Our  knowledge  of  the  vast  number  of  genera  and  species 
which  make  up  many  of  the  classes  of  the  animal  king- 
dom is  not  sufficient,  as  a  rule,  to  enable  us  to  group  all 
the  organisms  of  a  given  class  according  to  their  natural 
affinities,  but  in  a  Synoptic  Collection,  properly  chosen 
specimens  may  be  so  arranged  as  to  place  before  the  stu- 
dent a  more  or  less  satisfactory  demonstration  of  the 
principles  that  are  based  upon  the  genetic  relationships  of 
animals.  A  natural  classification  of  all  the  species  of  the 
whole  animal  kingdom  is,  indeed,  the  goal  of  the  natural 
philosopher,  but  this  goal  can  be  reached  only  through 
the  tireless  efforts  of  generations  of  devoted  truth  seekers. 

It  is  a  well  known  fact  that  certain  animals  are  simpler 
in  structure  than  others,  and  it  is  also  most  probable  that 
the  simplest  forms  living  to-day  are  the  nearest  repre- 
sentatives of  those  primitive  organisms  which  gave  rise 
through  countless  ages  and  generations  to  animals  of 
greater  and  greater  complexity.  For  this  reason  these 
simplest  forms  are  often  spoken  of  as  primitive  or  ances- 
tral forms.  Many  of  them  are  also  called  synthetic  or 
generalized  forms,  since  they  combine,  in  essentially  sim- 
ple condition,  certain  structural  characters  that  are  found 
more  developed  in  their  descendants,  and  because  this 

(9) 


10  SYNOPTIC    COLLECTION. 

further  development  was  probably  effected  by  a  process 
of  specialization. 

This  process  of  specialization  may  have  followed  along 
many  lines  of  development  in  the  successive  generations 
of  a  species. 

Thus,  for  example,  not  only  the  locomotive  organs  but 
also  the  mouth  parts,  sense  organs,  and  skeletal  structures 
may  have  become  differentiated,  while  corresponding  inter- 
nal changes  may  have  taken  place,  the  resulting  species 
possessing  manifold  organs  and  functions.  Such  animals 
are  broadly  differentiated  species,  becoming  so  by  the  law 
of  specialization  by  addition.  Secondly,  the  process  of 
specialization  may  have  followed  along  a  few  lines,  result- 
ing in  the  excessive  development  of  a  few  organs  and  the 
partial  or  complete  loss  of  others.  These  animals  are 
specialists  by  the  law  of  specialization  by  reduction  acting 
under  favorable  conditions.  Thirdly,  the  same  process 
under  the  thwarting  influence  of  an  extremely  unfavorable 
environment  may  have  tended,  not  towards  many  sided 
development  and  the  production  of  a  broadly  differentiated 
species ;  not  towards  the  excessive  development  of  a  few 
organs  with  the  loss  of  others  and  the  consequent  pro- 
duction of  a  more  specialized  species  ;  but  rather  towards 
a  gradual  diminution  in  the  size  of  the  organisms,  a  loss 
of  many  organs  and  functions,  and  finally  towards  the 
gradual  extinction  of  the  species  or  group.  Such  a  spe- 
cies we  shall  describe  as  reduced,  since  it  is  truly  an 
extreme  product  of  the  law  of  specialization  by  reduction. 
In  any  one  of  these  three  cases  mentioned  above  we  have 
originally  primitive  forms  giving  rise  to  secondary  forms, 
and  in  a  collection  based  upon  natural  relationships  the 
former  should  always  precede  the  latter.  We  have 
adhered  strictly  to  this  principle  in  the  Synoptic  Col- 
lection of  this  Museum,  so  far  as  the  present  state  of  our 
knowledge  would  permit. 

In  the  groups  of  the  Metazoa  or  animals  that  follow 
after  the  Protozoa,  and  Mesozoa,  the  development  of  the 


PROTOZOA.  1 1 

f  any  given  species  has  been  considered  a  more  or 
less  trustworthy  guide  for  determining  the  phylogeny,  or 
historic  evolution,  of  the  phylon  or  tribe  to  which  the 
animal  that  produced  the  egg  belonged.  This  egg,  or 
ovum,  as  generally  described,  is  a  cell  made  of  protoplasm 
and  containing  a  nucleus  within  which  is  a  nucleolus. 
It  is,  however,  reasonable  to  suppose  that  this  nucleated 
and  therefore  differentiated  condition  of  protoplasm  arose 
from  an  unnucleated  and  undifferentiated  condition,  and, 
therefore,  we  seek  for  what  may  be  called  the  ancestral 
stages  of  the  nucleated  egg.  If  these  stages  have  become 
obliterated  in  the  eggs  of  the  more  specialized  animals  by 
the  action  of  the  law  of  acceleration  in  development,  it 
would  seem  probable  that  they  might  be  represented  by 
the  unnucleated  adults  of  the  Protozoa,  and  that  a  study 
of  these  simplest,  one  celled  organisms,  and  of  the  spe- 
cializations leading  from  an  unnucleated  to  a  nucleated 
condition  of  protoplasm,  might  throw  light  not  only  on 
the  origin  of  the  nucleated  egg,  but  also  upon  the  natural 
classification  of  the  Protozoa.  Thirty  years  ago  it  would 
not  have  been  possible  to  attempt  such  a  classification  of 
this  subkingdom.  But  the  observations  and  experiments 
of  many  investigators  during  the  past  few  years  have 
thrown  strong  light  upon  the  structure  and  development 
of  many  species  and  the  possible  phylogenetic  history  of 
several  groups.  The  elaborate  work  of  Biitschli,  com- 
prising three  volumes  of  Bronn's  Thier-Reich,  and  the 
great  work  of  Haeckel, —  the  Challenger  Report  on  the 
Radiolaria, —  have  both  been  published  since  1880. 
Besides  these,  a  large  number  of  original  papers  and  sev- 
eral special  works  on  different  groups  have  appeared 
since  1874;  notable  among  these  are  the  writings  of  Gru- 
ber,  Hertwigand  Lesser,  Cienkowski,  Schultze,  Grenacher, 
Brandt,  Verworn,  Maupas,  Mereschkowsky,  Plate,  Hofer, 
and  of  Leidy,  W.  Saville  Kent,  Brady,  Dallinger  and 
Drysdale,  Lang,  E.  Ray  Lankester,  Hyatt,  Ryder,  Archer, 
Bessels,  Calkins,  Wilson,  and  others.  Although  we  have 


12  SYNOPTIC    COLLECTION. 

not  followed  any  one  author  in  the  arrangement  of  the 
Protozoa  of  the  Synoptic  Collection,  yet  we  are  chiefly 
indebted  to  the  above  named  investigators  for  the  facts 
upon  which  the  arrangement  is  based. 

The  Synoptic  Collection  of  this  Museum,  is  contained 
in  Room  E  of  the  Main  Hall.  The  two  central  floor 
cases  (A  and  B)  exhibit  the  classes  of  invertebrates, 
while  the  wall  cases  are  reserved  for  the  vertebrates. 
The  Protozoa  are  in  the  horizontal  part  of  section  i  of 
case  A.  These  are  represented  by  drawings,  models,  and 
fossils,  since  the  animals  living  to-day  are  mostly  micro- 
scopic. Beginning  with  the  simplest  Protozoan  organisms, 
as  represented  by  Plates  1-6,  we  pass  to  more  and  more 
differentiated  forms  until  we  reach  the  groups  represented 
by  Vorticella  and  Podophyra.  Beyond  these  and  under 
the  Sponges  are  the  Mesozoa,  represented  by  Volvox. 
All  the  specimens  and  plates  of  drawings  in  each  group 
are  numbered  in  a  continuous  series.  As  a  rule  we 
begin  at  the  lower  right  hand  corner  of  each  section,  and 
pass  to  the  left1  and  backward  in  the  horizontal  part,  and 
upward  in  the  erect  part,  ending  at  the  upper  left  hand 
corner.  Deviations  from  this  rule  are  owing  to  the  pecul- 
iar shape  or  the  large  size  of  the  specimens.  The  figures 
on  the  plates  are  also  numbered  consecutively  beginning 
with  the  lower  left  hand  corner  and  ending  with  the  upper 
right  hand  corner. 

1  This  arrangement  is  necessary  to  accord  with  the  arrangement 
adopted  throughout  the  Museum. 


PROTOZOA. 


13 


PROTOZOA. 

Section  i  (horizontal  part). 
SARCODINA.  —  MONERA. 

Scepticism  prevails  in  regard  to  the  existence  of  Hae- 
ckel's  Monera.  Nevertheless,  as  Calkins1  remarks,  the 
claim  of  Haeckel  "that  there  are  organisms  without 
nuclei  ....  although  it  rests  upon  negative  evidence,  can- 
not be  rejected  until  all  the  forms  considered  have  been 
shown  to  possess  them." 

It  is  readily  conceivable  that  non-nucleated  forms  were 
the  first  to  exist  in  a  remote  past,  and  that  these  antedated 
the  nucleated  forms  seem  a  reasonable  supposition.  Some 
of  these  non-nucleated  organisms  have  persisted,  it  would 
seem,  since  ancient  times,  although  it  is  probable  that  all 
modern  Protozoa  differ  in  some  respects  from  their  primi- 
tive ancestors.  Since  these  earliest  ancestors  were  made 
of  protoplasm  only,  being  wholly  without  hard  parts,  no 
record  of  their  structure  has  been  preserved  in  the  rocks. 
For  this  reason  we  must  begin  with  the  simplest  Protozoa 
living  to-day. 

In  PL  i,  figs.  i-6a,  is  represented  the  salt  and  fresh 
water  form,  Protamoeba primitiva  Hkl.,  and  in  PI.  2,  figs. 
i-4a,  a  species  of  marine  Protamoeba  (P.  schultzeana 
Hkl.).  There  are  many  and  strong  reasons  for  maintain- 
ing that  the  first  animal  life  which  existed  was  marine. 
The  first  Protamoeba  described  and  figured  by  Haeckel 
(PL  i,  figs.  i-6a)  was  found  in  fresh  water,  but  since 
then  Protamoeba  primitiva  Hkl.,  has  been  discovered  in 
salt  water.  With  our  present  knowledge  of  the  properties 

1  The  Protozoa,  1901,  p.  40.  (Columbia  University  Biological 
Series,  VI.) 


14  SYNOPTIC    COLLECTION. 

of  the  elements  of  inorganic  nature  it  is  possible  to  con- 
ceive of  the  origin  of  a  mass  of  protoplasm  like  the  young 
Protamoeba  (PL  i,  fig.  i).  This  is  seen  to  be  nearly  as 
large  as  the  adult  (fig.  2) ,  owing  probably  to  rapid  growth ; 
in  P.  schultzeana  HkL,  however,  the  young  form  (PI.  2,  fig. 
i)  is  smaller  than  the  full  grown  organism  (PL  2,  fig.  2). 
The  youthful  form  of  Protamoeba primitiva,  like  the  adult, 
is  a  homogeneous,  structureless  mass  of  protoplasm  or 
sarcode,  possessing  no  organs  nor  covering,  and  is  known 
as  a  cytode.  No  nucleus x  is  present,  and  no  non-con- 
tractile or  contractile  cavities  called  vacuoles. 

Protamoeba  schultzeana  differs  from  Protamoeba  primi- 
tiva by  having  the  protoplasm  differentiated  into  an  outer 
layer  or  ectosarc  and  an  inner  layer  or  endosarc,  both  of 
which  are  extended  to  form  irregular,  knobbed,  spherical 
continuations,  as  seen  in  the  drawings  (PL  2,  figs.  i~4a). 

Notwithstanding  the  extreme  simplicity  of  structure  of 
Protamoeba  prtmitiva,  the  organism  has  the  power  of  lo- 
comotion, as  is  well  shown  by  PL  i,  figs.  2,  3.  A  pro- 
longation of  the  body,  or  pseudopodium,  is  extended  and 
the  streaming  of  the  protoplasm  into  it  causes  the  animal 
to  creep  over  surfaces.  This  is  probably  one  of  the  sim- 
plest physiological  modes  of  motion,  and  results  in  pro- 
ducing a  crawling  type. 

The  power  of  taking  food  by  means  of  the  pseudopodia 
was  not  observed  by  Haeckel,  who  described  this  form, 
although  he  proved  that  small  particles  were  absorbed 
into  the  protoplasm  of  the  body.  In  other  species  of  the 
same  genus  the  pseudopodia  and  body  have  been  seen  to 
envelop  the  food  and  the  function  of  digestion  followed. 

1  Biitschli  considers  that  Protamoeba  (as  well  as  all  of  its  group 
of  Monera)  has  a  nucleus,  but  that  it  was  not  detected  at  the  time 
this  organism  was  studied,  on  account  of  the  imperfect  means  of  in- 
vestigation which  then  existed.  On  the  other  hand,  no  nucleus  has 
been  found  in  Protamoeba  vorax  by  Gruber  (stated  by  Rolleston  and 
Jackson,  Forms  of  Animal  Life,  ed.  2,  1888,  p.  916),  or  in  Archerina 
by  E.  Ray  Lankester  (Quart.  Journ.  Micr.  Sci.,  XXV,  1885,  p.  61), 
and  these  investigators  have  carried  on  their  researches  with  modern 
appliances  and  according  to  modern  histological  methods. 


PROTOZOA.  15 

It  may  be  that,  in  the  earliest  condition  of  living  pro- 
toplasm, nourishment  was  simply  taken  into  the  mass  by 
a  process  analogous  to  absorption,  and  that  the  additional 
strength  acquired  in  this  way,  together  with  a  subsequent 
deficiency  in  the  food  supply,  gave  rise  to  a  desire  to  go 
in  search  of  food  and  therefore  originated  the  function  of 
locomotion.  In  the  development  of  the  more  specialized 
animals  the. passive,  absorbent  stage  is  not  represented, 
so  that  the  function  of  locomotion  precedes  the  function 
of  taking  and  digesting  food. 

The  function  of  reproduction  is  shown  in  PL  i,  figs. 
4-6a,  also  in  PL  2,  rigs.  3~4a.  The  body  becomes  con- 
stricted (PL  i,  fig.  4),  and  this  constriction  continues  un- 
affected by  the  change  in  form  which  each  of  the  halves 
undergoes  until  only  a  mere  thread  connects  the  two 
parts  (PL  i,  fig.  5  ;  PL  2,  fig.  3)  ;  this  finally  separates 
and  each  half  rounds  itself  off  immediately  and  creeps 
away  as  an  independent  organism  (PL  i,  figs.  6,  6a ;  PL 
2,  figs.  4,  4a).  This  process  of  reproduction  is  known  as 
division  or  fission.  It  will  be  noticed  that  the  two  youth- 
ful forms  resemble  the  parent  before  constriction  of  its 
body  has  taken  place. 

We  cannot  fail  to  recognize  in  Protamoeba  an  organism 
performing  the  important  vital  functions  of  the  more  spe- 
cialized animals.  We  shall  presently  see  how  this  knowl- 
edge of  its  life  history  is  a  natural  introduction  to  the 
more  differentiated  Amoeba  (PL  9),  which  is  regarded  by 
all  biologists  as  an  animal;  and  for  this  reason  we  prefer 
to  place  the  Protamoeba  among  animals  rather  than 
among  plants  or  neutral  organisms. 

Portions  of  the  sea  bottom  at  great  depths  are  covered 
by  a  vast  gelatinous  mass  known  as  the  Bathybius  slime. 
This  slime  is,  in  part,  made  up  of  an  infinite  number  of 
protoplasmic  cytodes  of  various  sizes,  and  imbedded  in 
these  are  calcareous  bodies  called  coccoliths,  which  are 
now  considered  to  be  vegetable  in  origin  and  therefore 
foreign  to  the  true  Bathybius. 


16  SYNOPTIC    COLLECTION. 

PI.  3,  fig.  i,  represents  one  of  the  smaller  cytodes. 
showing  the  blunt  pseudopodia,  and  PL  3,  fig.  2,  one  of 
the  larger  cytodes  in  the  form  of  an  irregular  network  with 
the  imbedded  coccoliths,  greatly  magnified.  The  indefi- 
nite form  of  the  cytodes,  the  absence  of  organs  and  outer 
covering,  and  the  possession  of  blunt  pseudopodia,  to- 
gether with  the  fact  that  movements  have  been  observed 
in  the  protoplasm,  suggest  the  possibility  that  we  have 
here  a  vast  number  of  marine  Protamoeba-like  organisms; 
but  more  investigations  on  the  Bathybius  are  needed  be- 
fore its  exact  nature  and  relations  can  be  determined  with 
certainty.  It  was  called  a  mineral  deposit  by  Wyville 
Thomson,  its  discoverer,  but  was  considered  an  organic 
form  by  Huxley  and  Haeckel. 

If  now  the  crawling  marine  Protamoeba  should  adapt 
itself  to  the  life  of  a  free  swimmer  in  the  open  sea,  we 
might  expect  to  have  as  a  result  a  form  not  unlike  Pro- 
togenes  primordialis  Hkl.  (PI.  4,  fig.  i).  The  flattened 
body  of  the  creeping  Protamoeba  would  tend  to  become 
more  or  less  spherical  when  suspended  in  the  water  and 
the  simple,  blunt,  ever-changing  pseudopodia  might  de- 
velop into  the  long,  branching,  and  more  constant  pro- 
pelling organs  which  enable  the  animal  to  swim  rapidly 
through  the  sea.  Be  this  as  it  may,  we  certainly  recog- 
nize in  this  unnucleated  Protozoan  specialization  of 
structure  and  function,  and  we  find  a  correlation  existing 
between  habit  and  structure.  If  we  could  find  a  young 
form  (PI.  4,  fig.  2 ) 1  similar  to  Protogenes,  which  after 
growing  to  adult  size  divided  by  fission,  and  if  these 
zoons,2  instead  of  separating,  remained  together  for  a 
time  at  least,  connected  by  their  branching  and  anasto- 
mosing pseudopodia,  then  we  should  have  a  colonial  form 
like  Myxodictyum  sociale  Hkl.  (PI.  4,  fig.  3).  Here  we 

1  It  is  probable,  although  not  proved,  that  Myxodictyum  sociale 
Hkl.  arises  by  the  detachment  of  single  animals  like  PI.  4,  fig.  2. 

2  Zoon   is  substituted  for  individual.      For  reasons,   see   Hyatt, 
"  Larval  Theory  of  the  Origin  of  Cellular  Tissues,"  Proc.  Boston 
Soc.  Nat.  Hist.,  XXIII,  1884,  p.  46. 


PROTOZOA.  17 

have  a  Protozoan  that  is  probably  single  when  young  and 
colonial  when  adult,  which  illustrates  an  extremely  inter- 
esting phase  of  development  in  animal  life. 

The  Protamoeba,  Bathybius,  Protogenes,  and  Myxo- 
dictyum  belong  to  the  simplest  Monera;  other  genera  of 
this  group  illustrate  further  specialization  in  structure. 
Archerina  boltoni  Lankester  is  represented  in  PI.  5,  figs. 
1,2.  Fig.  i  may  be  the  form  that  issues  from  the  hard- 
ened case  or  cyst.  It  consists  of  a  spherical  body  with 
long,  motionless  pseudopodia  radiating  outward  from  the 
surface.  A  large  vacuole  is  seen  in  the  interior.  This 
organism  is  especially  interesting  because  it  contains 
chlorophyl.  The  latter  is  confined  to  a  single  or  bifid 
corpuscle.  No  nucleus  exists,  but  the  chlorophyl  cor- 
puscle appears  to  take  the  place  of  the  nucleus,  perform- 
ing a  similar  function  in  the  process  of  reproduction. 
The  corpuscle  usually  divides  into  four  parts  followed  by 
the  division  of  the  surrounding  protoplasm,  until  a  colony 
is  formed  (PI.  5,  fig.  2,  a  small  bit  taken  from  a  large 
colony).  This  colony  was  decolorized,  and  the  small 
chlorophyl  corpuscles  appeared  as  in  PI.  5,  fig.  3,  while 
the  large  ones  were  undergoing  division  (see  PI.  5,  fig.  4). 
The  Haeckelina  borealis  (PI.  6),  discovered  by  Meresch- 
kowsky,  shows  a  fixed  or  stationary  Moner.  The  long, 
solid  stem  by  which  it  is  attached  is  secreted  by  the  pro- 
toplasm, this  secretion  taking  place  constantly  on  one 
part  of  the  body  which,  when  the  stem  is  formed,  becomes 
the  lower  surface.  This  organism  is  without  nucleus  or 
vacuoles,  but  several  round,  strongly  refracting  balls  are 
present  in  the  protoplasm  which  are  probably  drops  of 
oil.  The  pseudopodia  are  short  and  delicate,  and  are 
scattered  over  the  whole  surface.1 

1  Biitschli  places  this  form  among  the  Heliozoa,  although  he  says 
vacuoles  are  wanting  and  presumably  a  nucleus,  while  there  is  no 
differentiation  of  the  protoplasm  into  an  outer  part,  or  ectosarc,  and 
inner  part,  or  endosarc.  Its  striking  resemblance  to  the  Heliozoan, 
Clathrulina,  will  be  seen  by  comparing  PI.  6  with  PL  43,  fig.  7,  but 
if  the  observations  already  made  are  accurate,  the  two  forms  are  not 
closely  related  genetically. 


18  SYNOPTIC    COLLECTION. 

An  unfilled  gap  exists  between  these  forms,  which  are 
among  the  more  undifferentiated  members  of  the  Monera 
and  the  Protomyxa,  which  Haeckel  considers  a  Moner 
and  Biitschli  a  Rhizopod.  No  nucleus  has  been  dis- 
covered in  Protomyxa,  and  for  this  reason  we  do  not  feel 
justified  in  placing  it  with  the  Rhizopods.  On  the  other 
hand,  the  habit  of  fusing  or  blending  with  other  zoons 
of  its  own  kind,  of  covering  itself  with  a  hardened  case  or 
cyst  and  passing  into  a  resting  state,  and  especially  of 
producing  flagellate  young,  makes  it  seem  not  improbable 
that  flagellate  unnucleated  adults  which  have  arisen 
through  adaptation  of  structure  to  habit  may  have  existed 
as  the  ancestors  of  Protomyxa.  This  may  be  the  case  or 
else  a  nucleus  may  be  found,  when  the  Protomyxa  can  be 
placed  among  the  Rhizopods  as  Biitschli  has  already  done. 

The  experiments  of  Gruber  on  Dimorpha  mtitans  (PL 
50,  figs.  1-9)  suggest  still  another  view,  namely,  that  the 
flagellate  condition  may  be  assumed  quickly  in  response 
to  the  need  for  rapid  motion.  Therefore,  the  flagellum 
in  many  cases  of  these  simpler  Protozoans  may  often  be 
an  adaptive  and  not  an  inherited  character. 

PL  7,  fig.  i,  represents  the  younger  stage  of  Protomyxa 
as  it  issues  from  the  cyst.  After  the  exit  it  adopts  the 
more  usual  crawling  motion,  thereby  assuming  the  Pro- 
tamoeba-like  form  (PL  7,  fig.  2)  and  showing  an  interme- 
diate stage  between  the  flagellate  and  the  Protamoeboid 
condition.  In  PL  7,  figs.  3,  4,  the  Protamoeboid  state  is 
more  pronounced.  PL  7,  fig.  5,  is  a  single  zoon  showing 
the  function  of  nutrition,  a  Navicula  being  assimilated  by 
the  plasma  of  the  body.  After  nourishment  is  taken, 
vacuoles  or  cavities  filled  with  fluid  and  without  distinct 
walls  begin  to  appear  which  are  not  found  in  the  young 
(PL  7,  figs.  1-3).  A  form  like  PL  7,  fig.  5,  was  seen  to 
fuse  with  a  similar  zoon.  PL  7,  fig.  6,  represents  three 
or  four  zoons  that  have  fused  together.  PL  7,  fig.  7,  is 
an  adult  formed  by  the  fusion  of  several  zoons,  and  PL  7, 
fig.  8,  an  adult  after  being  well  fed.  The  vacuoles  are 


PROTOZOA.  19 

present  in  considerable  numbers;  these,  however,  are 
non-contractile  and  inconstant  in  position.  The  pseudo- 
podia  branch  and  anastomose.  Food  material — diatoms 
and  the  like  —  is  found  in  the  protoplasm  of  the  body". 
The  adult  draws  in  the  pseudopodia  and  covers  itself  with 
a  cyst  (PI.  7,  fig.  9).  A  structureless,  glassy  membrane 
surrounds  the  orange-red  contents.  PI.  7,  rig.  10,  repre- 
sents another  stage  more  advanced  in  which  the  interior 
mass  has  become  divided  into  many  orange-red  balls.  In 
PI.  7,  fig.  1 1,  the  cyst  has  opened  and  the  flagellate  young 
are  issuing.  This  completes  the  cycle  of  the  life  of  the 
Protomyxa. 

PI.  7,  fig.  12,  is  an  under-fed  adult.  We  describe  it 
here  as  an  illustration  of  the  fact  that  unfavorable  condi- 
tions produce  changes  in  structure  which  may  tend 
towards  the  reduction  of  the  zoon.  The  vacuoles  have 
decreased  in  number  and  the  pseudopodia  only  slightly 
branch  and  anastomose.  The  structural  changes  induced 
by  the  small  quantity  of  food  taken  may  be  transient,  as 
in  the  case  figured  above  where  the  under-fed  zoon  might 
become  like  the  over -fed  specimen  (PI.  7,  fig.  8)  by  giv- 
ing it  a  larger  supply  of  food.  If,  however,  the  cause  of 
structural  change,  be  it  an  insufficient  diet  or  any  other 
cause  unfavorable  for  the  development  of  the  zoon,  were 
continued  through  successive  generations,  the  result  prob- 
ably would  be  the  production  of  a  smaller,  weaker,  per- 
haps distorted  form,  and  finally  the  total  extinction  of  the 
species.  Such  a  species  may  be  called  a  reduced  or  a 
suppressed  species,  since  it  has  suffered  diminution  in 
organs  and  efficiency.  It  is  also  often  called  simple,  but 
in  order  to  avoid  the  mental  confusion  which  arises  when 
this  word  simple  is  applied  both  to  primitive  and  to 
reduced  forms,  we  prefer  to  restrict  its  use  to  the  former 
which  have  comparatively  few  organs  and  these  oftentimes 
in  rudimentary  or  developing  condition.  There  are  other 
reasons  for  doing  this.  While  it  may  be  true  that  there  are 
reduced  animals  which  cannot  be  distinguished  from  the 
primitively  simple  forms,  yet  in  the  greaf  majority  of 


20  SYNOPTIC    COLLECTION. 

cases  they  bear,  at  some  time  of  life  and  especially  when 
young,  indubitable  proofs  of  their  evolutionary  history. 
These  proofs  or  revelations  of  their  past  condition  make 
the  reduced  forms  more  complicated  in  reality  than  at 
first  appears,  and  it  is  these  structural  characters  which 
should  receive  a  clear  descriptive  term  free  from  ambig- 
uity, since  it  is  these  characters  which  are  of  very  great 
importance  in  tracing  the  phylogenetic  history  of  animals. 

The  habit  of  fusion  which  has  been  observed  in  Pro- 
tomyxa  is  probably  one  important  cause  of  the  origin  and 
differentiation  of  the  organ  known  as  the  nucleus.  We 
cannot  suppose,  however,  that  this  process  of  differentia- 
tion was  rapid,  so  that  a  well  developed  nucleus  was  made 
at  once,  but  there  were  doubtless  transitional  organisms  in 
which  the  nucleus  was  in  the  process  of  forming.  We 
had  arrived  at  this  conclusion  before  having  seen  the 
work  of  Gruber x  on  Pachymyxa  hystrix. 

In  this  form,  Pachymyxa  hystrix  (PI.  8,  figs.  3-7  ;  fig. 
3,  a  living  specimen  containing  brown  food  material,  and 
fig.  6,  the  same  probably  in  the  process  of  division), 
Gruber  was  never  able  to  observe  a  nucleus,  but  he  saw 
scattered  in  the  protoplasm  a  large  number  of  dark 
colored  granules  which  became  red  when  treated  with  a 
reagent  (PI.  8,  fig.  5).  Specimens  were  also  seen  where 
the  colored  granules  were  surrounded  by  a  colored  zone 
of  protoplasm  so  that  they  looked  like  little  swarm  buds 
(PI.  8,  fig.  4),  but  the  exit  of  these  small  bodies  was  not 
observed.  This  form  of  Pachymyxa  has  an  outer  layer 
differentiated  into  thickly  set  rods,  between  which  the 
pseudopodia  are  thrust  out.  This  is  seen  in  PI.  8,  figs. 
3-5  and  7;  in  the  last  figure,  fig.  7,  a  small  portion  is 
magnified,  showing  the  rods  and  one  pseudopodium 
drawn  while  in  the  coloring  fluid. 

iZeitschr.  f.  wiss.  Zool.,  XL,  1884,  p.  122.  On  this  subject 
Gruber  says  we  may  suppose  that  a  stage  preceded  the  formation  of 
the  typical  Rhizopod  nucleus,  when  little  grains  of  nuclear  substance 
lay  scattered  through  the  whole  protoplasm,  and  that  these  only 
came  together  later  to  form  the  real  nucleus. 


PROTOZOA.  21 

In  the  naked  and  more  simple  form  (PI.  8,  figs,  i,  2  — 
probably  a  variety  of  the  same  species)  there  is,  however, 
no  such  differentiation  of  the  outer  part;  fig.  i  shows 
the  brown  food  material  in  the  interior  and  the  pseudo- 
podia,  and  fig.  2  is  a  specimen  colored  and  showing 
probably  one  stage  of  division  in  which  the  organism  is 
separating  into  two  parts.  The  nuclear  grains  are  seen 
in  this  figure,  as  also  in  fig.  5. 

It  is  reasonable  to  suppose  that  a  transitional  organism 
exists,  or  has  existed,  in  which  the  young  stage  has  nu- 
clear grains  and  the  adult  a  well  formed  nucleus,  but  we' 
have  seen  no  such  species  described  or  figured. 


SARCODINA.  —  RHIZOPODA. 

The  probable  intermediate  forms  just  mentioned  lead 
naturally  to  the  group,  Amoebina,  represented  by  the 
Amoeba protens  Leidy  (PI.  9,  figs.  i-n).  Here  we  have 
a  typical  Rhizopod  with  the  organs  and  functions  peculiar 
to  such  an  animal.  PL  9,  fig.  i,  is  probably  the  young 
of  this  species  and  fig.  2  presumably  an  older  stage.  In 
both  the  young  and  the  adult  (fig.  3)  the  protoplasm  has 
become  more  or  less  differentiated  into  a  clear  outer  layer, 
the  ectosarc,  and  an  inner  granular  portion,  the  endosarc. 
When,  however,  one  observes  by  the  aid  of  a  microscope 
the  granular  endosarc  flowing  into  the  clear  ectosarc  and, 
as  it  were,  taking  possession  of  it,  one  becomes  convinced 
that  there  is  no  constant  line  of  demarcation  between  the 
two.1 

1  According  to  Leidy  (Fresh-water  Rhizopods  of  North  America, 
U.  S.  Geol.  Surv.  Terr.,  XII,  1879,  p.  24},  Dr.  Wallich  states  that 
the  ectosarc  is  due  to  a  temporary  and  partial  coagulation  of  the  en- 
dosarc coming  in  contact  with  the  water  in  which  the  animal  lives, 
and  it  again  reverts  to  the  mass  of  the  endosarc  within  the  body. 
The  process  reminds  one  of  the  cooling  of  a  molten  mass  of  metal 
at  the  sides  of  a  crucible,  and  the  melting  away  again  of  the  crust  as 
it  is  stirred  from  the  sides  into  the  remainder  of  the  molten  mass 
within. 


'  SYNOPTIC    COLLECTION. 

From  this  point  of  view  the  Amoeba  is  interesting  as 
offering  an  intermediate  position  between  organisms  that 
are  absolutely  unprotected,  like  Protamoeba  and  others, 
and  those  that  are  permanently  covered  with  hardened 
protoplasm  or  with  a  chitinous  or  a  calcareous  shell. 

Within  the  endosarc  is  a  nucleus  (fig.  3,  white;  fig.  4, 
the  same  colored)  which  consists  of  a  nuclear  membrane, 
nuclear  fluid,  often  called  sap,  and  suspended  in  the  latter 
a  large  number  of  grains  which  allow  themselves  to  be 
colored  and  are  therefore  called  chromatin  grains.  The 
non-contractile  vacuoles  are  present,  and  also  a  contractile 
or  pulsating  vacuole,  or  vesicle,  as  it  is  often  called  (fig. 
3,  pink  in  color)  which  is  more  or  less  constant  in  posi- 
tion, and  which  may  have  arisen  phylogenetically  from 
the  former,  as  suggested  by  Haeckel.1 

Besides  the  vacuoles,  nucleus,  and  minute  crystals  that 
are  often  found  in  the  protoplasm,  there  are  grains  of 
sand  which  the  animal  has  taken  up  in  crawling  over  sur- 
faces, but  which  it  has  not  formed  into  an  outer  covering 
or  shell.  The  pseudopodia  are  blunt,  like  those  of  Pro- 
tamoeba, and  are  extended  in  the  act  of  performing  the 
function  of  locomotion  (fig.  5).  This  figure  shows  also 
the  transient  tendency  to  an  anterior  and  posterior  region 
of  the  body  which  is  sometimes  observable.  The  Amoeba 
is  a  crawling  type,  although  now  and  then  it  floats  and 
swims.  At  such  times  its  body  becomes  rounded  and  its 
pseudopodia  radiate  in  different  directions,  as  seen  in  fig. 
6,  which  illustrates  clearly  the  correlation  of  structure  and 
habit.  The  power  of  taking  food  is  finely  shown  in  figs. 
3  and  7.  In  fig.  7  a  pair  of  pseudopodia,  acting  like  the 
finger  and  thumb  of  the  human  hand,  have  come  together 
at  their  ends,  entirely  encircling  an  active  Infusorian, 
Urocentrum.  Another  recently  captured  Urocentrum  is 
seen  within  the  body  of  the  Amoeba.  In  fig.  3,  a  diatom 

!Jena.  Zeitschr.,  IV,  1868.  Engl.  transl.,  Quart.  Journ.  Micr. 
Sci.,  IX,  1869,  p.  114. 


PROTOZOA.  23 

has  been  caught,  and  is  probably  taken  into  the  body 
through  the  extension  or  flowing  of  the  ectosarc  over  it. 

After  the  food  is  digested  the  excrement  is  sometimes 
ejected  simply  by  the  unfolding  of  the  protoplasmic  body, 
and  at  other  times  is  discharged  from  the  posterior  part 
of  the  body,  as  seen  in  fig.  5b. 

As  already  stated,  the  contractile  vacuole  is  a  cavity 
which  is  filled  with  fluid  and  which  contracts  and  dilates 
quite  regularly.  According  to  the  experiments  of  Grif- 
fiths,1 it  performs  at  times  an  excretory  function  similar 
to  that  of  the  kidneys  in  the  more  specialized  animals, 
but  it  is  interesting  to  note  that  at  other  times  no  waste 
nitrogenous  matter  is  found. in  the  vacuole,  and  it  is  most 
likely,  as  stated  by  Griffiths,  that  the  organ  in  its  primi- 
tive condition  performs  more  than  one  kind  of  work,  com- 
bining, it  may  be,  a  respiratory  with  an  excretory  function. 
Experiments  on  the  more  differentiated  Protozoa,  such  as 
Paramoecium  and  Vorticella,  proved  that  the  contractile 
vacuole  in  these  forms  performed  the  function  of  a  true 
kidney,  the  product  excreted  being  the  same  as  in  the 
most  specialized  animals. 

Circulatory  movements  of  the  endosarc  have  already 
been  spoken  of  under  the  head  of  structure,  and  are  men- 
tioned here  again  since  they  belong  with  the  physiological 
activities  of  the  Amoeba.  PI.  9,  fig.  8,  represents  the 
granular  endosarc  flowing  into  the  hyaline  ectosarc,  the 
direction  of  the  current  being  indicated  by  arrows.  The 
susceptibility  of  the  organism  to  external  forces  is  shown 
in  different  ways;  whenever  the  glass  slide  on  which  the 
Amoeba  is  crawling  is  touched  or  jarred,  its  pseudopodia 
are  partially  or  wholly  drawn  in  and  a  more  or  less  spher- 
ical form  is  assumed,  as  seen  in  fig.  9.^  This  irritability 

1  Proc.  Roy.  Soc.  Edinburgh,  XVI,  iSSS-'Sg,  p.  131. 

2  Amoeba  radiosa.    According  to  C.  Scheel,  Amoeba  radiosa  is  the 
young   of   A.  proteus.      See    his    Beitrage   zur    Fortpflanzung   der 
Amoben,  in  C.  von  Kupffer's  Festschrift  zum  siebenzigsten  Geburts- 
tag,  1899,  pp.  569-580. 


24  SYNOPTIC    COLLECTION. 

of  protoplasm  may  give  rise  in  time  to  nerve  force  which 
ultimately  in  the  more  specialized  animals  becomes  local- 
ized in  a  nervous  system,  and  which  manifests  itself  in 
consciousness  and  will  power. 

The  Amoeba  proteus  usually  has  but  one  nucleus  (fig.  3), 
but  sometimes  a  specimen  is  found  with  two  nuclei  (fig.  5). 
Reproduction  in  this  species  probably  takes  place  by  fis- 
sion. PI.  9,  fig.  10,  is  a  supposed  Amoeba  proteus  in  the 
act  of  dividing.  The  separation  of  the  thread  connecting 
the  two  parts  occurred  in  ten  minutes  after  the  stage 
represented  in  the  figure. 

Gruber's  important  experiments  on  Amoeba  proteus  and 
other  Protozoa,  in  order  to  determine  the  part  played  by 
the  nucleus  in  reproduction,  prove  that  by  artificial  divi- 
sion only  the  portion  possessing  the  nucleus  is  capable 
of  reproducing  itself.  The  Amoeba  was  divided  as 
shown  in  PI.  9,  fig.  n,  and  the  portion  marked  a  lived, 
while  b  drew  in  its  pseudopodia  and  died.  After  many 
experiments  Gruber  concludes  that  it  is  an  incontrover- 
tible fact  that  the  nucleus  is  the  species-preservative  con- 
stituent of  the  cell,  and  that  to  it  is  justly  ascribed  the 
highest  importance  in  the  processes  of  fecundation  and 
inheritance.1  If  it  is  true  that  the  continuance  of  the  life 
of  the  species  depends  upon  the  nucleus,  then  it  follows 
that  in  passing  from  the  Protamoeba  to  the  Amoeba  a 
change  has  taken  place  in  the  protoplasmic  organism. 
The  generative  power  manifested  by  the  cytode  is  cer- 
tainly an  indication  of  the  existence  of  a  generative  sub- 
stance making  up  a  part  at  least  of  the  cytode,  and  it 
would  seem  as  if  this  substance  had  become  localized  in 
the  nucleus  of  the  Amoeba  to  form  a  distinct  and  species- 
preservative  organ.  The  remarkable  differentiations  of 
the  nucleus  which  are  found  in  succeeding  and  more 

1  Ann.  and  Mag.  Nat.  Hist.,  (5),  XVII,  1886,  p.  473.  Translated 
from  the  Berichte  der  naturforschenden  Gesellschaft  zu  Freiburg  i. 
B.,  i,  1886.  See  also  Hofer,  Jena.  Zeitschr.,  XXIV  (Neue  Folge, 
XVII),  Heft  i,  1889,  P-  1O5;  and  Morgan,  Regeneration,  1901,  p. 
65  (Columbia  University  Biological  Series,  VII). 


%  PROTOZOA.  25 

specialized  genera  of  Protozoa  tend  to  strengthen  this 
hypothesis. 

It  is  probable,  although  it  is  not  yet  proved,  that 
Amoeba  proteus  forms  swarm-buds  in  the  shape  of  little 
Amoebae. 

PI.  9  is  instructive  since  it  places  before  the  student  a 
simple  organism  capable  of  performing  in  a  simple  way 
the  vital  functions  of  the  most  specialized  animals. 

Many  interesting  differentiations  of  structure  are  shown 
in  other  species  of  Amoeba.  The  marine  Amoeba  (A. 
obtecta)  crawls  with  extreme  slowness.  According  lo 
Gruber  these  Rhizopods  do  not  exhibit  any  tendency  to 
undertake  migrations,  and  therefore  when  the  conditions 
are  favorable  they  lie  together  in  great  numbers  and  thus 
form  regular  societies.1 

In  Amoeba  polypodia  M.  Schultze  (PI.  10,  figs.  i-8a), 
which  may  have  one  or  several  nuclei,  the  pseudopodia 
are  numerous,  and  are  more  equal  throughout  their  length, 
approaching  the  thread-like  organs  of  many  Foraminifera. 
The  process  of  fission  is  shown  in  figs,  i— 8a,  which  illus- 
trate more  clearly  the  different  stages  of  development 
than  preceding  figures.  The  specimen  observed  had  one 
nucleus.  The  division  of  this  organ  took,  place  in  one 
minute  and  a  half,  and  that  of  the  body  in  eight  and  a 
half  minutes,  so  that  ten  minutes  were  required  for  the 
whole  process.  Figs.  2-8a  are  drawn  in  outline,  showing 
the  division  of  the  nucleus  and  protoplasmic  body  and 
also  the  increase  in  the  number  of  vacuoles. 

There  are  organisms  closely  related  to  these  Amoebae 
which  seem  to  throw  light  on  the  origin  of  the  flagel- 
lum,  and  to  point  to  the  probability  that  certain  Rhizo- 
pods have  given  rise  to  the  Mastigophora  (—  Flagellata.) 
According  to  Calkins,2  however,  there  is  no  conclusive 

1  Zeitschr.  f.  wiss.  Zool.,  XXXVIII,  1883,  p.  56.     Engl.  transl., 
Ann.  and  Mag.  Nat.  Hist,  (5),  XI,  1883,  p.  276. 

2  The  Protozoa,  1901,  p.   105.     (Columbia  University  Biological 
Series,  VI.) 


26  SYNOPTIC    COLLECTION. 

evidence  to  support  the  view  that  Rhizopods  are  more 
primitive  than  Flagellata,  or  vice  versa.  He  says  :  ;'  Their 
mutual  affinities  are  very  close,  and  together  they  stand  as 
the  most  primitive  forms  of  modern  Protozoa." 

While  this  may  be  true,  a  much  more  consistent  ar- 
rangement can  be  made  if  one  begins  with  the  Sarcodina, 
as  Calkins  has  done,  and  passes  to  the  Mastigophora 
(  =  Flagellata)  and  then  to  the  most  specialized  Infusoria 
(see  p.  53). 

The  whip-bearing  Rhizopod  (PI.  n,figs.  1,2)  repre- 
sents an  adult  which  combines  the  flagellum  with  the 
Amoeboid  pseudopodia.  This  flagellum  is  eight  or  ten 
times  the  length  of  the  body.  When  the  motion  changes 
from  creeping  to  swimming,  the  body  lengthens  as  seen 
in  fig.  2. 

Amoeba  quinta  l  shows  a  marked  specialization  of  the 
nucleus.  PL  12,  fig.  i,  is  a  young  form  with  eight  nuclei. 
Whether  the  youngest  stage  has  one  nucleus  cannot  be 
stated.'2  PL  12,  fig.  2,  represents  an  adult  with  twenty- 
four  nuclei  (more  existed  but  were  omitted  for  the  sake 
of  clearness),  and  the  species  may  have  hundreds,  this 
increase  taking  place,  as  the  figures  show,  with  the  growth 
of  the  animal.  PL  12,  fig.  2a,  represents  the  nucleus  as 
it  appears  before  staining,  which  shows  a  differentiation 
in  structure  from  the  nucleus  of  Amoeba  proteus  (PL  9, 
fig.  3).  The  outer  membrane  lies  over  a  peripheral  layer 
of  granules,  and  the  central  portion  is  filled  with  a  mass 
which  appears  granular.  When  colored,  the  nucleus  has 
the  appearance  seen  in  PL  12,  fig.  2,  which  is  much  more 

1  This  species  was  described  by  Gruber  as  Amoeba  proteus  (Zeit- 
schr.  f.  wiss.  Zool.,  XXXVIII,   1883.  p.  382),  but  afterward  was 
found  by  him  to  be  Amoeba  quinta  (ibid.,  XLI,  1885.  p.  205).     See 
his  description  of  Amoeba  proteus  (ibid.,  XLI,  1885,  p.  216,  pi.  XV, 
figs.  43-45-) 

2  Gruber,  Zeitschr.  f.  wiss.  Zool.,  XLI,   1885.     This  author  says 
that  what  Btitschli  has  shown  as  such  appears  to  belong  to  another 
species  of  Amoeba. 


PROTOZOA.  27 

specialized  than  the  colored  nucleus  of  A.  proteus  (PI.  9, 
fig.  4) .  Inside  of  the  dark  colored  outer  layer  is  a  zone 
of  nuclear  sap,  while  the  central  mass  we  may  probably 
indicate  as  a  nucleolus.1  In  PI.  12,  fig.  2,  four  of  the 
twenty-four  nuclei  are  in  the  process  of  division,  and  the 
figure  is  very  instructive  as  showing  the  origin  of  the 
many-nucleated  forms.  The  process  is  probably  rapid, 
and  this  may  account  for  the  fact  that  few  naturalists 
have  been  fortunate  enough  to  observe  and  draw  it. 

In  Pelomyxa  palustris  Greef  we  have  an  Amoeba-like 
form  when  young'2  (PI.  13,  figs.  1-4).  Many  of  these 
Amoebae  came  from  a  dead  Pelomyxa.  After  moving 
about,  they  became  more  quiet  (PI.  14,  fig.  5),  some  con- 
tracted themselves  into  a  spherical  or  pear-shaped  body 
(PI.  13,  figs.  6,  7),  after  which  a  long  vibrating  thread  was 
stretched  out  (PI.  13,  fig.  8),  and  the  Amoeba  became 
transformed  into  a  flagellate  animal.  After  rapid  rotat- 
ing movements  this  young  flagellate  organism  passed  out 
of  sight,  "rowing  with  the  front,  quickly  swinging  whip," 
so  that  unfortunately  its  further  development  was  not 
observed.  Whether  the  flagellate  young  remained  a  flag- 
ellate organism,  or  whether  it  passed  into  the  unflagellate 
adult  (PL  13,  fig.  9)  cannot  be  stated.  In  the  adult,  the 
tendency  towards  an  anterior  and  a  posterior  region  of 
the  body  is  marked.  The  animal  stretches  itself  out  and 
moves  in  curves,  turning  the  forward  end,  now  to  the 
right,  now  to  the  left  (PI.  13,  fig.  9).  At  the  posterior 
end  there  is  a  glassy  disc-like  expansion.  PI.  13,  fig.  10, 
is  a  magnified  portion  of  the  body.  Many  nuclei  are 
present  which  may  be  converted  into  the  "shining  bod- 

iGruber,  Zeitschr.  f.  wiss.  Zool.,  XXXVIII,  1883.  According 
to  Calkins,  the  Protozoan  cell,  with  possibly  one  exception,  has  no 
true  nucleolus  comparable  with  the  nucleolus  of  the  Metazoan  cell. 
What  has  been  so  called  is,  according  to  this  author,  either  func- 
tional chromatin  that  has  aggregated  into  a  mass,  or  an  intranuclear 
sphere  or  division  center  (see  The  Protozoa,  1901,  p.  253). 

2  Greef ,  Arch.  f.  mikr.  Anat.,  X,  Supplement,    1874,  p.  51. 


28  SYNOPTIC    COLLECTION. 

ies"  1  that  give  rise  to  the  Amoeba-like  young  (PI.  13,  figs. 
1-4).  The  little  rods  (PI.  13,  fig.  10)  are  thought  to  be 
parasitic  plants.  The  streaming  of  the  endosarc  with  its 
vacuoles,  rods,  etc.,  into 'the  hyaline  ectosarc  is  well  shown 
in  the  drawing. 

If  the  flagellate  condition  is  a  normal  stage  in  the  devel- 
opment of  Pelomyxa  and  not  a  parasitic  organism  as  main- 
tained by  some  naturalists,  the  species  is  an  exceedingly 
interesting  one.  Observations  on  such  forms  as  the  whip- 
bearing  Rhizopods,  Pelomyxa,  and  also  those  of  Gruber 
on  Dimorpha  mutans  show  that  the  amoeboid  and  flagel- 
late conditions  are  marked  in  these  less  specialized  organ- 
isms by  extreme  variability,  depending,  it  may  be,  upon 
the  need  for  slow  or  rapid  motion.  The  flagellum  arising 
in  this  way  as  an  adaptive  character  may  become  fixed  in 
the  organization  and  finally  inherited  as  a  permanent 
organ,  which  would  seem  to  be  the  case  in  the  Mastigo- 
phora  (=  Flagellata). 

The  group  of  Amoebina  represented  by  DifHugia  (PI. 
14,  fig.  i)  not  only  possesses  many  nuclei,  but  these  have 
become  differentiated  so  that  each  contains  one  or  more 
nucleoli  (fig.  la).  In  addition  to  this  specialization  in 
structure  the  protoplasm  is  not  only  capable  of  taking  up 
sand  grains,  like  that  of  the  Amoeba  proteus,  but  it  is  able 
to  lay  a  part  of  these  on  the  surface  for  a  protective  cover- 
ing or  shell. 

PI.  14,  fig.  i,  is  a  vertical  section  through  the  shell  and 
body  of  Difflugia  urceolata  Carter.  The  hyaline  ectosarc 
extends  out  into  the  pseudopodia  which  are  stretched  from 
the  opening.  In  the  protoplasm  of  the  interior  are  seen 
the  nuclei  colored  red  (PI.  14,  fig.  la,  nucleus,  uncolored 
and  magnified),  besides  sand  and  bits  of  nourishment. 
Figs.  2-5  illustrate  the  division  and  shell  formation  of  the 
same  species.  In  order  to  determine  how  the  shell  was 

*For  views  on  this  subject  see  Greef,  Arch.  f.  mikr  Anat.,  X,  Sup- 
plement; also  Gruber,  Zeitschr.  f.  wiss.  Zool.,  XLI,  1885. 


PROTOZOA.  29 

formed,  Verworn1  isolated  a  specimen  and  gave  it  splinters 
of  blue  glass.  He  observed  repeatedly  that  the  Difflugia 
crept  by  the  splinters,  its  pseudopodia  pushing  them  away 
instead  of  taking  them  up.  After  a  time  a  Cypris  passed 
and  irritated  the  pseudopodia,  which  caused  a  sticky  secre- 
tion to  form  on  their  surface,  so  that  pieces  of  glass  were 
caught  in  it  and  were  then  taken  into  the  body  with  the 
pseudopodia. 

Afterward  Verworn  irritated  the  pseudopodia  with  a 
needle;  the  surface  became  rough  and  took  up  glass 
which  before  it  did  not  do.  The  splinters  were  really 
drawn  into  the  protoplasm  so  that  the  interior  contained 
a  little  heap  of  them.  These  observations  tend  to  prove 
that  the  origin  of  the  shell  of  Difflugia  urceolata  is 
mechanical  and  largely  a  matter  of  accident. 

Later  experiments  upon  Difflugia  lobostoma  Verworn,'2 
tend  to  prove  that  the  animal  does  not  exhibit  a  conscious 
choice  in  the  taking  up  of  material  for  its  shell,  nor  does 
there  seem  to  be  any  calculation  in  regard  to  the  quantity 
of  sand  grains  or  glass  splinters  needed.  Sometimes  a 
mass  was  taken  and  then  thrown  out  in  order  apparently 
to  take  up  more  —  a  desire  to  get,  it  would  seem,  rather 
than  to  use. 

Verworn  saw  two,  three,  and  even  five  zoons  of  this 
species  of  Difflugia  in  conjugation.  He  proved  by  experi- 
ment that  two  zoons  might  touch  each  other  for  a  long 
time  without  blending,  while  other  zoons  united  with  the 
fusion  of  the  protoplasm.  Experiments  were  made  to 
cause  zoons  to  blend  by  keeping  two  close  together,  but 
were  unsuccessful,  and  the  author  considers  that  it  is 
proved  indubitably  that  every  zoon  cannot  blend  with 
every  other.  On  the  other  hand,  two  zoons  which  were 
in  conjugation  were  separated  but  these  came  together 
again,  showing  that  one  must  exert  a  directive  influence 
upon  the  other  or  the  two  upon  each  other.  The  cause 
may  be  of  a  chemical  nature,  as  maintained  by  Verworn. 

1  Zeitschr.  f.  wiss.  Zool.,  XLVI,  1888,  Heft  IV,  p.  455. 

2  Zeitschr.  f.  wiss.  Zool.,  L,  Heft  3,  1890,  p.  449. 


30  SYNOPTIC    COLLECTION. 

The  process  of  division  is  illustrated  by  PL  14,  figs.  2-5. 
First  a  swelling  (fig.  2)  is  seen  at  the  mouth  of  the  shell 
which  approaches  the  spherical  form  (fig.  3).  The  pro- 
toplasmic swelling  reached  in  time  the  size  of  the  parent 
form  and  a  mass  of  glass  splinters  was  seen  entering 
the  newly  formed  half  (fig.  4)  where  the  protoplasm  with 
the  splinters  showed  a  slowly  flowing  movement.  In  the 
most  advanced  stage  of  division  the  protoplasm  which 
had  curved  forward  had  taken  the  form  of  a  Difflugia 
shell,  and  the  glass  splinters  were  placed  in  a  layer  upon 
its  surface  (fig.  5).  The  new  half  did  not  seem  to  have 
a  firm  shell,  as  the  splinters  of  glass  were  still  quite 
loosely  joined  to  one  another.  The  next  day  the  zoon 
separated  from  the  parent,  its  shell  assumed  the  charac- 
teristic form,  while  the  pieces  of  blue  glass  were  united 
by  means  of  a  binding  material  which  was  still  quite 
colorless,  and  which,  after  some  days,  began  to  assume  a 
darker  brownish  shade.  Verworn  succeeded  in  taking  off 
the  shell  and  obtained  the  naked  Difnugia.  Several  of 
these  shell-less  specimens  he  kept  for  three  weeks,  and 
no  attempt  was  made  on  the  part  of  the  animal  to  make 
a  new  shell.  He  therefore  concludes,  after  many  experi- 
ments, that  the  species  of  Difnugia  do  not  reconstruct  an 
injured  shell  nor  make  another  when  one  has  been 
removed. 

The  Foraminifera  are  Rhizopods  in  which  the  pro- 
toplasm is  differentiated  into  ectosarc  and  endosarc,  and 
the  nucleus  has  a  membrane,  a  distinct  chromatin  net- 
work with  one  or  more  nucleoli  (Biitschli).  In  certain 
forms,  like  Trochammina  (=  Rotating)  inflata,  and  in 
Ovulina,  one  half  of  the  nucleus  has  been  found  to  con- 
sist of  chromatin,  the  other  of  a  non-staining  substance. 
The  less  differentiated  Foraminifera  possess  a  one  cham- 
bered shell,  and  are  single  forms,  while  the  most  differ- 
entiated have  a  complex,  many  chambered  shell;  each 
chamber,  it  may  be,  representing  a  zoon,  and  if  so  the 

1  Throughout  this  Guide  synonyms  are  placed  in  parenthesis. 


PROTOZOA.  31 

many  chambered  shell  represents  a  colony.  Many  natur- 
alists, however,  hold  that  this  is  not  a  colony,  but  is  one 
zoon  with  a  polythalamous  shell.  In  the  case  of  Difflugia 
just  described,  the  bud  represented  another  zoon  that  in 
this  species  separates  from  the  parent  form,  but  which  in 
the  complex  Foraminifera  remains  attached  and  makes 
its  own  covering.  In  the  arrangement  of  the  Foraminif- 
era the  single  forms  are  given  first  when  this  is  possible, 
and  afterward  the  colonial  forms  which  may  have  arisen 
from  them  phylogenetically. 

Saccammina  is  a  simple,  hollow,  spherical  Rhizopod 
which  usually  occurs  single  (PI.  15,  fig.  i,  S.  sphaerica 
M.  Sars).  Sometimes  several  shells  adhere  by  their  ex- 
ternal surfaces  and  the  openings  remain  distinct,  as  shown 
in  PI.  15,  fig.  2,  a  form  which  has  received  the  name  of 
Saccammina  socialis.  This  association  of  zoons  where 
there  is  no  organic  connection  reminds  one  of  the  "  so- 
cieties "  of  the  marine  Amoeba  obtecta  (see  p.  25)  and 
of  the  association  of  the  cytodes  of  Bathybius.  In  fig.  3 
(S.  sphaerica}  we  have  such  a  rude  attempt  at  a  colony 
that  it  seems  to  be  an  initial  effort.  These  zoons  are 
connected  by  protoplasmic  extensions,  or  stolons.  The 
largest  chamber  was  the  primordial  one,  and  was  fastened 
between  two  stones  ;  the  succeeding  zoons  then  arose  as 
buds  which  formed  their  shells  in  an  irregular  manner, 
and  the  terminal  chamber  was  merely  a  mass  of  sand  grains 
with  large  interstitial  openings  through  which  passed  the 
pseudopodia. 

The  specimen  (No.  16)  and  PI.  17,  figs,  i— 8,  represent 
Astrorhiza  liwicola  Sandahl,1  described  by  Bessels  under 

1  This  name  was  given  by  Sandahl  (Ofvers.  Kongl.  Vetenskaps- 
Akad.  Forhandl.,  XIV,  p.  299)  in  1857,  and  is  retained  on  account 
of  priority.  Brady  places  Astrorhiza  among  the  Foraminifera.  Ac- 
cording to  Sandahl  there  are  many  nuclei,  but  these  are  figured  by 
him  as  occurring  among  the  grains  of  the  pseudopodia.  an  unusual 
position  for  nuclei.  Bessels,  whose  observations  are  more  extended, 
neither  figures  nor  describes  a  nucleus.  Until  positive  knowledge 
is  obtained  we  place  it  provisionally  among  the  Foraminifera. 


32  SYNOPTIC    COLLECTION. 

the  name  of  Haeckelina  gigantea.  PI.  17,  fig.  i,  represents 
the  young  Astrorhiza  which  has  arisen  by  a  forcible  sepa- 
ration of  a  piece  of  the  arm,  it  being  probable  that  new 
animals  or  zoons  arise  from  the  swollen  ends  of  the  arms. 
It  is  Amoeba-like,  and  is  without  a  shell.  The  drawing 
represents  it  just  after  its  separation ;  PI.  17,  fig.  2,  is  the 
same  ten  hours  later  ;  fig.  3,  the  same  somewhat  con- 
tracted ;  fig.  4,  the  same  four  days  after  separation  (one 
projection  sends  out  a  number  of  delicate  thread-like 
pseudopodia  which  branch  slightly)  ;  fig.  5  is  an  older 
stage  in  which  the  dark  brown  protoplasm  is  not  yet  cov- 
ered with  a  shell ;  fig.  6  represents  one  still  further  de- 
veloped which  appears  to  be  on  the  point  of  making  a 
shell.  The  process  of  specialization  continues  until  the 
full  grown  organism  (.fig.  7)  has  the  shell  completed. 
The  material  of  which  it  is  made  is  usually  sand  or  mud. 
It  has  a  varying  number  of  continuations  from  which  ex- 
tend the  pseudopodia.  Fig.  8  is  the  drawing  of  a  colony 
of  seven  adult  zoons  united  by  their  arms  which  in  this 
case  serve  as  stolons. 

According  to  Neumayr 1  the  irregular  agglutinating 
Foraminifera,  such  as  the  Astrorhizidae,  have  given  rise 
to  the  regular  agglutinating  forms,  and  these  in  turn  to 
the  imperf orated  and  the  perforated  calcareous  Forami- 
nifera. 

Re.ophax  bacillaris  Brady  (No.  18),  and  R.  nodulosa 
Brady  (No.  19),  are  more  regular  than  Astrorhiza,  though 
they  are  rough  on  the  surface  and  are  usually  made  of 
sand  with  a  silicious  cement. 

Cornnspira  involvens  Reuss.  (PI.  20,  fig.  i),  is  one  of 
the  imperforate  limy  shells.  It  has  a  variable  number  of 
undivided  convolutions  making  a  circular  flattened  shell. 
Another  species,  C.  striolata  Brady  (PI.  20,  fig.  2), 
broadens  out  and  passes  over  into  a  form  resembling 
Peneroplis,  soon  to  be  described. 

!Die  Stamme  des  Thierreiches,  I,  1889,  p.  198. 


PROTOZOA.  38 

The  Miliolidae  are  represented  by  the  mounted  speci- 
mens (No.  21).  The  term  Miliola  may  be  used  very 
properly  in  a  generic  sense  to  comprehend  a  great  variety 
of  closely  associated  forms  having  the  same  general  type 
of  structure  (Brady).  It  is  reasonable  to  suppose  that  a 
single  form,  Uniloculina  or  Loculina,  exists,  or  has  existed 
in  the  past,  although  no  such  form  has  been  described. 
The  Biloculina  (No.  21)  has  two  chambers  visible  exter- 
nally, and  each  successive  segment  encloses  the  younger 
ones  on  the  same  side. 

The  group  of  Foramjnifera  is  a  very  remarkable  one 
for  studying  gradational  forms.  Here,  to  the  inexpressi- 
ble delight  of  the  student,  all  artificial  systems  break  down. 
"It  is  only,"  says  Brady,  "as  we  learn  to  recognize  the 
fact  that  among  the  Rhizopoda  the  so  called  '  species  '  rep- 
resent no  more  than  terms  of  a  series  of  which  very  fre- 
quently every  intermediate  link  can  be  supplied  that  we 
arrive  at  any  just  idea  of  their  relationship." l  Among  the 
more  specialized  groups  of  animals  many  of  the  interme- 
diate forms  are  unfortunately  wanting,  but  these  doubtless 
either  exist  at  the  present  time  or  have  existed  in  the  past, 
and  if  the  lesson  taught  by  the  Foraminifera  could  be 
impressed  upon  the  student  at  the  beginning  of  his  studies, 
he  would  be  less  inclined  to  draw  sharp  lines  of  demarca- 
tion, since  these  are  arbitrary  and  unauthorized  by  nature. 

No.  22  and  PI.  23,  figs.  1-7,  represent  Peneroplis,  of 
which  Brady  says  there  is  no  genus  of  Foraminifera 
embracing  so  great  a  variety  of  external  form  in  which  the 
morphological  sequence  is  at  once  so  simple  and  so  com- 
plete.2 

PL  23,  fig.  i,  is  a  young  specimen  of  Peneroplis  show- 
ing the  spiral  mode  of  growth.  Fig.  2  is  an  adult  of  the 

1  Challenger  Report  on  the  Foraminifera,  IX,  1884,  p.  49. 

2  For  other    figures  showing  the  variety  in  external  form  of  this 
genus,  see    Brady,  Challenger    Report  on  the    Foraminifera,  IX, 
1884,  PI.  XIII;  also   Carpenter,  Introd.  to   Study  of  Foraminifera, 
PI.  VII. 


34  SYNOPTIC    COLLECTION. 

Dendritine  variety  in  which  the  last  chamber  is  taking  the 
rectilinear  mode  of  growth.  Fig.  3  is  the  Spiroline  vari- 
ety of  the  same  genus  in  which  a  considerable  portion  of 
the  shell  is  rectilinear.  Fig.  4  (Peneroplis  arietinus 
Batsch.),  fig.  5  (longitudinal  section  of  the  same),  and 
fig.  6  (Peneroplis  cylindraceus  Lamarck)  show  the  gradual 
diminution  of  the  spiral  portion  and  the  increase  of  the 
rectilinear  part.  These  figures  illustrate  the  changes 
from  a  spiral  to  a  rectilinear  mode  of  growth  in  different 
species  of  one  genus,  while  the  slides  No.  24  (specimens 
obtained  from  the  sand  of  the  Bahamas)  and  PI.  25,  figs. 
1-5,  exhibit  the  changes  from  a  spiral  to  an  annular  growth 
in  one  species.  Orbiculina  adimca  F.  u.  M.  PL  2 5,  fig.  6, 
is  a  section  giving  the  interior  of  the  shell.  It  shows  that 
the  primordial  chamber  was  globular  and  that  subse- 
quently spiral  growth  took  place  followed  by  annular 
growth. 

Unusual  interest  attaches  to  the  species  Orbitolites  ten- 
nis sima  Carpentet  (PI.  26).  Beginning  as  a  globular 
shell  it  passes  into  the  undivided  Cornuspira  condition 
which  is  clearly  marked  in  the  young;  the  later  convolu- 
tions are  sometimes  constricted  at  opposite  points,  thus 
indicating  the  Milioline  stage.  Next  the  spiral  stretches, 
after  the  fashion  of  a  Peneroplis.  The  chambers  extend 
themselves  extraordinarily  in  breadth,  until  by  the  meeting 
of  the  lateral  ends  a  ring  is  formed  around  the  spiral  part 
of  the' shell,  as  in  Orbiculina.  These  annular  rings  or 
chambers  are  divided  by  cross  walls  into  a  great  number 
of  chamberlets.  Finally  the  complex  structure  with  many 
additional  covering  cells  or  chambers  peculiar  to  Orbito- 
lites is  developed.1 

Miliota,  Peneroplis,  Orbiculina,  and  Orbitolites  belong 
to  the  calcareous  group  of  Porcellanous  Foraminifera. 
The  calcareous  group'  with  a  hyaline  or  glassy  appear- 

1  For  further  information  see  Carpenter,  Rep.  Chall.  Exped., 
Zool.,  VII,  part  XXI,  1883,  pp.  1-49,  pis.  I-VIII. 


PROTOZOA.  35 

ance  is  represented  in  the  Collection  both  by  fossils  and 
by  series  of  drawings.  The  simplest  or  most  elemen- 
tary structure  in  this  latter  group  is  to  be  found  in  the 
shell  of  Lagena  (PI.  27,  figs.  1,2).  Fig.  i.  Lagenaglobosa 
Montagu,  shows  the  globular  shell  so  common  as  the 
ground  form  of  the  Foraminifera,  and  fig.  2,  Lagena  laevis 
Montagu,  represents  a  flask-shaped  modification  of  the 
primitive  form.  The  shell  of  Lagena  is  a  single  chamber 
with  a  terminal  opening.  The  walls  are  calcareous  and 
finely  perforated  for  the  exit  of  the  pseudopodia.  This 
genus  like  others  exhibits  great  variation. 

Nodosavia  (PI.  27,  figs.  3-5,  No.  28,  N.  soluta  Reuss.) 
consists  of  chambers  united  in  a  straight  or  curved  line, 
with  the  opening  in  the  center  of  the  terminal  chamber. 
PI.  27,  fig.  3.  is  Nodosaria  simplex  Silvestri,  consisting  of 
two  chambers  in  a  straight  line,  and  fig.  4  is  another  spe- 
cies of  the  same  genus  (Nodosaria  subtertenuata  Schwager) 
composed  of  several  chambers.  Fig.  5,  Nodosaria  (= 
Dentalina)  farcimen  Soldani,  has  more  chambers  and  the 
shell  shows  a  tendency  to  curve. 

The  group  represented  by  Globigerina  is  one  of  great 
interest  since  the  ooze  of  portions  of  the  deep  sea  is 
largely  made  up  of  the  shells  of  these  Foraminifera. 
Although  existing  in  such  vast  numbers  to-day,  both 
Globigerina  and  Orbulina  (see  p.  36)  have  been  dis- 
covered recently  in  the  ancient  Cambrian  formation  of 
New  Brunswick.1  Here  they  occur  well  preserved  in 
shales  and  in  phosphate  nodules.  Sufficient  investiga- 
tions, however,  have  not  been  made  to  prove  beyond 
doubt  that  this  ancient  Orbulina  is  the  primitive  ancestral 
form  of  Globigerina. 

Cayeux's  paper2  is  interesting  in  this  connection.     He 

1  Matthews,    Trans.   N.  Y.  Acad.  Sci.,    XII,   1893;   also  XIV, 
March,  1895. 

2  Sur  la  presence  de  restes  de  Foraminiferes  dans  les  terrains  pre*- 
Cambriens  de  Bretagne.      1894.      See  also  review  of   M.  Cayeux's 
paper  by  G.  F.  Matthews,  Amer.  Geol.,  XV,  1895,  p.  146. 


36  SYNOPTIC    COLLECTION. 

has  found  one-chambered  shells  in  the  pre-Cambrian 
rocks  of  Brittany,  but  is  unable  to -determine  with  cer- 
tainty whether  they  are  primitive  Foraminifera  or  Radio- 
laria  ;  he  thinks  they  may  be  the  latter  and  therefore  does 
not  figure  them.  They  are  doubtless  older  than  those 
discovered  in  New  Brunswick,  as  pointed  out  by  Mat- 
thews, since  they  occur  in  an  older  series  of  rocks  and  are 
very  much  smaller  in  size.  Associated  with  the  unilocu- 
lar  forms  are  Foraminifera  consisting  of  from  two  to  seven 
chambers  (PL  29,  figs.  1-6)  and  belonging  to  the  Perfor- 
ata.  Fig.  i  shows  a  two-chambered  shell,  figs.  2  and  3, 
three-chambered  shells,  figs.  4  and  5,  two  different  forms 
of  four-chambered  shells;  fig.  6  is  the  only  shell  possess- 
ing more  than  four  chambers  that  M.  Cayeux  has  found. 
The  irregularity  and  imperfect  attempts  of  these  primitive 
Perforata  to  make  a  symmetrical  shell  remind  one  of  the 
similar  efforts  and  results  among  the  I mperforata  already 
figured  and  described. 

The  microscopic  slide  No.  30  represents  the  Globige- 
rina  ooze  from  the  deep  sea  off  Cape  Hatteras  obtained 
by  the  U.  S.  S.  Albatross,  in  1883.  Although  the  Glo- 
bigerina  shells  predominate  in  it,  yet  a  number  of  other 
genera  are  also  represented.  PI.  31  is  a  beautiful  draw- 
ing taken  from  the  Narrative  of  the  Challenger  Report 
(Vol.  i,  part  2,  PI.  N,  fig.  10.  p.  926)  of  Globigerina  ooze 
seen  by  reflected  light.  This  was  dredged  from  a  depth 
of  1900  fathoms  in  lat.  21°  38'  N..  long.  44°  39'  W.  Slide 
No.  32  exhibits  Globigerina  shells  dredged  from  the  At- 
lantic. No.  33  is  the  rosy  Globigerina  rubra  d'Orbigny. 
PI.  34,  fig.  i,  is  the  young  of  a  bottom  specimen  of  Glo- 
bigerina bulliodes  d'Orbigny,  which  does  not  possess 
spines;  PL  34,  fig.  2,  the  adult,  showing  more  chambers, 
and  fig.  3,  a  view  of  the  same,  showing  the  large  opening 
of  the  last  chamber. 

We  have  already  pointed  out  that  doubtless  Globigerina 
arose  from  a  single  hollow  sphere  such  as  Orbulina 
(slide  No.  35)  appears  to  be  when  observed  externally  ; 


PROTOZOA.  37 

but  the  internal  structure  of  many  species  of  this  genus 
shows  it  to  be  more  specialized  than  Globigerina.  In 
slide  No.  36  a  number  of  Orbulina  shells  are  seen  with 
Globigerina-like  shells  inside.  (The  broken  yellow  speci- 
men on  the  slide  is  probably  another  genus.)  PI.  37,  fig. 
i,  is  Orbulina  universa  d'Orbigny,  in  which  the  Globige- 
rina-like shell  in  the  interior  is  not  wholly  covered  by  the 
exterior  spherical  shell.  Fig.  2,  a  surface  specimen, 
shows  the  covering  entire  but  thin,  so  that  the  inner  shell 
can  *be  easily  seen  through  it.  Fig.  3  is  the  Globigerina- 
like  shell  from  which  the  outer  Orbuline  sphere  has  been 
removed.  The  shell  is  provided  with  spines,  like  most 
surface  specimens,  and  its  chambers  are  partly  or  wholly 
filled  with  .protoplasm.  In  fig.  4,  a  bottom  specimen,  the 
inner  shell  is  not  seen,  owing  to  the  thickness  of  the  wall. 
Fig.  5  is  an  old  bottom  specimen  in  which  the  inner  shell 
does  not  exist  but  the  wall  is  laminated,  giving  the 
appearance  when  seen  under  the  microscope  of  spheres 
within  spheres.  This  laminated  appearance  is  observable 
in  some  of  the  specimens  in  the  microscppic  preparation 
No.  36.  According  to  the  observations  of  Shacko,1  which 
were  made  on  bottom  specimens,  only  the  young  Orbu- 
linae  have  Globigerina-like  shells,  while  in  very  large  and 
old  bottom  specimens  they  do  not  occur. 

From  the  observations  made  on  Globigerina  and  Orbu- 
lina it  may  be  possible  that  we  have  here  only  one  genus. 
In  such  a  case,  the  youngest  or  nepionic  stage  would  be 
represented  by  a  single  thin-walled  hollow  sphere ;  the 
adolescent  or  neanic  stage  by  several  spheres  fastened 
together ;  the  mature  or  ephebic  stage  by  several  united 
spheres  completely  enclosed  in  the  last  globular  chamber ; 
and  the  old  age  or  gerontic  stage  by  a  single  hollow 
sphere,  the  thick  wall  of  which  is  laminated.  Either  this 
is  the  case  or  else  Globigerina  is  the  more  primitive, 
ancestral  form,  which  in  course  of  time  was  developed 

!Arch.  f.  Naturgeschichte,  XLIX,  I,  1883. 


38  SYNOPTIC    COLLECTION. 

into  the  Orbulina  that  possesses  Globigerina  characters 
in  youth  and  loses  them  in  age. 

In  PI.  38,  figs.  1,2,  Hastigerina  murrayi  Wy.  T.,  which 
belongs  to  the  Globigerina  group,  is  represented.  The 
shell  is  thin  and  possesses  spines  (fig.  i).  The  proto- 
plasm of  the  living  animal  envelops  the  shell,  taking  the 
peculiar  form  of  bubble-like  extensions,  and  thrown  out- 
ward beyond  these  are  the  extremely  long  pseudopodia 

(fig-    2). 

The  group  of  Nummulitidae  is  the  most  differentiated 
of  the  Foraminifera.  The  mounted  specimen  No.  39, 
Fusilina,  is  exclusively  fossil.  The  shell  is  bilaterally 
symmetrical.  The  chambers  extend  from  one  end  of  the 
shell  to  the  other,  and  each  convolution  encloses  the  pre- 
vious whorl.  The  walls  of  the  chambers  are  usually  single, 
and  there  are  no  interseptal  canals. 

Nummulites  is  represented  in  the  Collection  by  speci- 
mens (Nos.  40,  41).  No.  40  shows  two  whole  shells,  and 
between  these  a  horizontal  and  a  vertical  section  ;  back 
of  these  single  specimens  are  two  pieces  of  Nummulitic 
limestone ;  one  showing  fresh  surfaces,  while  the  other 
has  been  weathered  by  the  action  of  the  carbon  dioxide 
and  moisture  in  the  air  so  that  the  shells  stand  out  more 
prominently.  No.  41  is  remarkable  for  its  size,  being  a 
giant  of  its  kind.  The  internal  structure  is  shown  in  PI. 
42.  The  figure  at  the  left  is  a  horizontal  section  of 
Nummulites  granules  a  d'Arch.,  showing  the  double  walls 
between  the  chambers  and  the  canal  system.  The  two 
central  figures  are  Nummulites  laevigata  Lam.;  one  the 
whole  shell  and  the  other  a  vertical  section  showing 
chambers  and  walls.  The  figure  at  the  right  is  Num- 
mulites mamillata  d'Arch.,  with  a  portion  of  the  outer 
shell  removed. 


PROTOZOA.  39 


SARCODINA. —  HELIOZOA. 

One  of  the  most  familiar  examples  of  the  Heliozoa  is 
Actinophrys  sol  Ehr.  (PL  43,  figs.  1-3).  Fig.  i  is  the 
young  stage  observed  by  Kent,  which  possessed  a  flagel- 
lum.  While  swimming  it  projects  blunt  pseudopodia 
from  all  sides  (fig.  2).  Its  motions  then  become  slower, 
the  flagellum  is  withdrawn,  when  suddenly  thread-like 
organs  are  put  out  in  every  direction  and  the  animal  is 
transformed  into  the  adult  Actinophrys  (fig.  3).  If  the 
naked  spherical  body  of  a  typical  Rhizopod  should  re- 
main constant  in  form,  and  the  pseudopodia  should  radi- 
ate as  long  thread-like  organs  and  preserve  this  character 
essentially  unchanged,  then  we  should  have  the  Actino- 
phrys  in  outward  appearance.  In  the  Heliozoa  there 
may  be  one  or  many  nuclei.  In  Actinosphaerium,  a 
Heliozoan  closely  related  to  Actinophrys,  from  one  to  two 
hundred  nuclei  are  not  uncommon,  and  this  large  number 
in  the  adult  is  reached  from  one  nucleus  or  a  few  nuclei 
in  the  young  (Biitschli).  Actinophrys  increases  by  fission, 
and  this  sometimes  gives  rise  to  a  colony.1 

PI.  43,  fig.  4,  represents  a  young  embryo  of  Clathrulina 
elegans  Cienkowski2  which  soon  develops  into  the  form 
represented  by  fig.  5.  Its  striking  resemblance  at  this 
stage  to  Actinophrys  is  at  once  apparent.  Like  that 
Heliozoan  it  is  without  a  stem  or  a  skeleton.  In  fig.  6 
these  have  been  developed,  the  stem  being  secreted  first, 
but  both  are  as  yet  nearly  colorless.  Fig.  7  is  the  sta- 
tionary adult  with  its  stem  (only  part  of  which  is  shown 
in  the  drawing)  and  skeleton.  The  pseudopodia  extend 
in  all  directions  from  the  openings  of  the  shell.  After  a 
time  these  are  drawn  in  and  fission  takes  place,  each  prod- 

1  For  views  in  regard  to  the  process  of  conjugation  of  Actino- 
phrys and  the  Heliozoa  in  general,  see   Btitschli,   Bronn's  Thier- 
Reich,  I,  1881,  p.  317. 

2  See  Arch.  f.  mikr.  Anat.,  Ill,  1867,  p.  311. 


40  SYNOPTIC    COLLECTION. 

uct  of  the  fission  becoming  encysted  within  the  shell. 
Fig.  8  shows  four  cysts,  which  in  time  are  ruptured, 
allowing  the  embryos  to  slip  out. 

The  process  of  development  observed  by  Hertwig l 
differed  somewhat  from  the  above.  He  saw  the  division 
of  the  body  with  the  formation  of  flagellate  young  (PI. 
44,  fig.  i).  Each  swarmer  possessed  a  nucleus  and  sev- 
eral contractile  vacuoles,  while  in  the  forward  end  it  was 
provided  with  two  whips.  About  half  an  hour  after  leav- 
ing the  parent,  it  settled  perpendicularly  upon  an  object, 
took  on  a  spherical  form  and  a  naked  Clathrulina  re- 
sulted. The  stem  had  its  origin  in  a  depression  of  the 
body  which  is  visible  on  the  surface  as  a  sharply  defined 
circle  (seen  in  PI.  44,  fig.  2,  in  the  center  of  the  draw- 
ing). It  grows  long,  as  represented  in  fig.  3,  which  is  a 
naked  Clathrulina  before  the  shell  is  formed. 


SARCODINA.  —  RADIOLARIA. 

We  may  turn  with  a  feeling  of  assurance  to  the  primi- 
tive forms  of  Radiolaria  discovered  by  M.  L.  Cayeux  2  in 
pre-Cambrian  rocks  as  the  remote  ancestral  forms  of 
Radiolaria  living  to-day.  These  minute,  silicious  shells 
remained  practically  unchanged  during  the  metamorphism 
of  the  surrounding  rock.  The  primitive  Radiolaria  were 
spherical,  spineless,  and  some  had  an  imperfectly  trellised 
skeleton.  Of  those  that  were  symmetrical  Cenosphoera 
(PI.  45,  fig.  i,  x  1350;  fig.  2,  section  of  the  same)  was 
one  of  the  most  generalized.  The  characteristic  network 
is  seen  in  these  shells  with  perfect  clearness.  Though 
found  in  pre-Cambrian  and  Silurian  rocks,  this  genus 
occurs  at  the  present  time  both  on  the  surface  and  at 

1  See  Arch.  f.  mikr.  Anat.,  X,  Supplement,  1874,  p.  2. 

2  Bull.    Soc.    Geol.    de    France,    36    Sen,    XXII,    1894,    p.    197. 
Compte  Rendu  Soc.  Geol.  de  France,  May,  1894,  p.  Ixxix.     See  also 
Amer.  Geol.,  XV,  1895,  p.  146. 


PROTOZOA.  41 

great  depths  of  the  sea.  The  figures  of  Haeckel 1  show 
that  this  genus  and  several  other  genera  of  the  Radiolaria 
have  remained  essentially  unchanged  since  protozoic 
times.  Some  of  the  Radiolaria  have  spines,  as  seen  in 
PI.  45,  figs.  3-5.  Fig.  3,  Xiphosphoera,  has  two  equal 
spines;  fig.  4,  Staurosphoera,  has  four;  while  fig.  5, 
Acanthosphoera,  has  numerous  spines  at  the  nodes  of  the 
lattice  work,  though  only  three  have  been  preserved. 
The  basket  form  is  seen  in  Tripodiscium  (PL  45,  fig.  6), 
while  in  fig.  7  (which  belongs  to  the  section  of  the 
Dicyrtida,  though  the  family  is  not  determined)  the  shell 
is  divided  into  three  parts  with  numerous  spines. 

It  has  been  pointed  out  by  Haeckel  that  the  simple 
skeletonless  Heliozoan,  Actinophrys,  might  give  rise  to 
the  simple  shell-less  Radiolarian,  Actissa  princeps  Hkl. 
(PI.  46,  fig.  2),  the  stem-form  from  which  probably  the 
whole  group  of  Radiolaria  has  descended.  The  young 
Actissa  (fig.  i)  possesses  one  nucleus  and  is  a  flagellate 
form.  This  passes  probably  into  the  Actinophrys  stage 
which  unfortunately  has  not  been  observed.  Afterward 
a  membrane,  known  as  the  central  capsule,  forms,  which 
is  wholly  absent  in  the  young.  The  possession  of  this 
organ  separates  the  adult  and  more  specialized  Actissa 
from  Actinophrys,  and  is  the  peculiar  and  marked  charac- 
teristic of  a  Radiolarian.  PI.  46,  fig.  2,  is  the  adult. 
The  large  round  nucleus  is  seen  in  the  center  with  its 
nucleolus.  Around  the  nucleus  is  finely  granulated  pro- 
toplasm containing  many  clear  spherical  vacuoles.  These 
parts  are  contained  in  the  porous  central  capsule  ;  outside 
of  the  capsule  is  seen  the  jelly  envelope  or  calymma 
which  in  the  figure  is  yellow  but  colorless  in  the  living 
Radiolarian.  It  is  indeed  seldom  visible  in  the  living, 
freshly  taken  animal  when  observed  in  sea  water,  but 
since  it  does  not  readily  become  colored,  its  size  and  form  • 
can  be  made  out  definitely  by  placing  the  specimen  in 

1  Challenger  Report,  Zool,  XVIII. 


42  SYNOPTIC    COLLECTION. 

coloring  matter.  The  calymma  is  pierced  by  the  long 
radial  pseudopodia,  which  arise  outside  of  the  central 
capsule.  Late  in  the  life  of  the  adult  the  nucleus  divides 
into  a  large  number  of  nuclei,  as  seen  in  fig.  3a,  which  is 
a  diagrammatic  drawing  of  one  half  of  a  central  capsule 
of  an  older  specimen  than  fig.  2,  the  other  half  being  like 
it,  of  course,  at  this  stage  of  development.  These  nuclei 
together  with  a  part  of  the  surrounding  protoplasm  are 
transformed  into  the  flagellate  young  (fig.  3b,  a  diagram- 
matic view  of  one  half  of  a  central  capsule  in  a  more 
advanced  stage  of  development  than  fig.  3a). 

Actissa  is  a  single  form  like  most  of  the  Radiolaria. 
As  has  been  stated,  it  never  secretes  a  skeleton,  but 
many  Radiolaria  make  silicious  shells  of  rare  beauty  and 
great  complexity.  The  microscopic  preparation  (No.  47), 
when  seen  under  a  high  power,  shows  delicate  lattice- 
work forms  known  under  the  familiar  name  of  Polycys- 
tina,  which  was  given  by  Khrenberg  to  that  part  of  the 
Radiolaria  described  by  Haeckel  as  the  Spumellaria  and 
Nasellaria.  These  shells  were  taken  from  the  famous 
Polycystine  marl  of  Barbadoes  in  the  Antilles  which 
belongs  to  the  Miocene  period,  and  which  is  the  richest 
of  all  the  Radiolarian  deposits. 

Living  Radiolaria  are  represented,  greatly  magnified,  in 
PI.  48,  figs.  1,2.  In  fig.  i,  Thalassophysa  pelagica?  the 
delicate  pseudopodia  radiate  in  all  directions  from  the 
shell.  Fig.  2,  Theopilium  cranoides?  shows  these  and 
also  the  basket-like  form  and  delicate  lacework  of  the 
shell. 

The  colonial  Radiolaria  are  represented  by  Collozoum 
inerme  Hkl.  (PI.  49,  figs.  i-io).  Figs.  1-3  represent  the 
young.  Here  we  find  for  the  first  time  different  kinds  of 
zoons  and  this  differentiation  in  structure  is  suggestive  of 


1  Thalassicolla  pelagica  in  Haeckel's  Monograph. 

2  Eucyrtidium  cranoides  in  the  Monograph. 


PROTOZOA.  43 

a  differentiation  in  the  processes  which  have  produced  the 
zoons.  Fig.  i  is  known  as  an  isospore ;  it  is  provided 
with  a  whip,  a  homogeneous  nucleus  of  uniform  constitu- 
tion, and  a  little  rod-like  crystal.  Figs.  2  and  3  represent 
the  anisospores  (fig.  2  the  large  macrospore  and  fig.  3  the 
smaller  microspore)  which  are  never  produced  by  the  less 
specialized  Actissa.  These  are  provided  with  a  whip,1 
a  heterogeneous  nucleus  of  two-fold  constitution,  and  fat 
granules,  but  the  crystal  is  often  wanting.  Unfortunately 
all  attempts  have  failed  to  follow  the  development  of 
the  flagellate  young  to  the  typical  Radiolarian  condition 
represented  by  Actissa.  It  is  probable,  however,  that 
the  phenomenon  of  accidental  fusion  of  different  zoons 
observable  in  the  simpler  Rhizopods  has  given  rise  in  the 
colonial  Radiolaria  to  the  phenomenon  of  genetic  union 
or  conjugation,  and  that  the  macrospore  and  microspore 
unite ;  if  this  is  true  we  may  have  here  the  simplest  form 
of  sexual  reproduction.  After  this  possible  union  it  is 
probable  that  a  single  form  arises  like  Actissa  which 
becomes  a  colony  by  the  division  of  the  nucleus,  the  prod- 
ucts of  the  division  remaining  united  as  seen  in  fig.  4, 
which  is  a  young,  unarticulated  colony.  Fig.  5  is  a  piece 
of  a  young  colony  showing  how  the  many  central  capsules 
(represented  by  red  dots  in  fig.  4)  have  arisen.  There 
are  eight  of  these  capsules,  two  of  which  are  in  the  act  of 
dividing.  The  nucleus  is  seen  in  different  stages  of  divi- 
sion. Around  the  central  capsules  extends  the  jelly  like 
calymma  (blue  in  the  figure)  comparable  with  the  jelly 
envelopes  (yellow  in  the  figure)  of  Actissa.  Numerous 
vacuoles  and  yellow  cells  are  seen  in  the  calymma.  The 
latter  contain  starch  and  are  unicellular  yellow  algae  which 
live  with  many  Radiolaria.  True  to  their  plant  nature, 
these  yellow  cells  give  out  oxygen  which  is  eagerly  taken 
by  the  Radiolarian,  while  the  latter,  equally  true  to  its  ani- 

1  Brandt  says  they  possess  most  probably  two  whips  (see  Fauna 
und  Flora  des  Golfes  von  Neapel,  XIII,  p.  167). 


44  SYNOPTIC    COLLECTION. 

mal  nature,  gives  forth  carbon  dioxide.  This  supplemen- 
tary relation  where  there  is  a  mutual  dependence  of  the 
one  upon  the  other,  is  known  as  symbiosis  and  will  be 
found  to-  occur  among  other  more  specialized  animals. 

The  division  of  the  nucleus  takes  place  early  in  life  and 
this  is  a  fact  of  great  significance.     The  law  of  accelera- 
tion in  development  which  has  been  demonstrated  in  many 
groups  of  the  Metazoa,  may  have  acted  in  this  case,  caus- 
ing the    characteristic  late    nuclear   division    peculiar   to 
the  single  Radiolaria,  like  Actissa,  to  appear  early  in  the 
life  of  the  zoon.     After  the  division  the  process  of  spe- 
cialization is  carried  on  in  a  most  interesting  manner,  as 
shown  in  figs.  6-9,  and  results  finally  in  the  formation  of 
the    asexual   isospores    and    the    probably   sexual    aniso- 
spores.     Fig.  6  is  a  zoon  in  the  act  of  forming  isospores. 
The  original  central  nucleus  has  divided  into  many  nuclei, 
and  its  place  has  been  taken  by  a  large  oil  globule.     The 
nuclei  lie  close  together  but  do  not  press  upon  each  other 
sufficiently  to  be  flattened  into  polyhedrons.     The  crystals 
first  appear  like  lengthened  granules  and  one  is  laid  close 
to  a  nucleus.     Gradually  they  grow  into  the  form  shown 
in  fig.  6.     In  fig.  7,  a,  b  (a  diagrammatic  representation  of 
later  stages  in  the  process),  the  nuclei  and  crystals  have 
arranged  themselves  near  the  periphery,  while  the  large 
oil  globule  remains  in  the  center.     Finally  disintegration 
takes  place  and  the  isospores  appear.     Fig.  8  is  a  dia- 
grammatic representation  of  the  process  of  forming  aniso- 
spores  drawn  from  balsam  preparations.     In  early  stages 
(fig.  8a,  fig.  9)  irregular  groups  of  differentiated  nuclei 
occur  in  spherical  masses  of  plasma  (fig.  9  shows  a  group' 
of  three  nuclei  in  such  a  spherical  mass) ,  and  in  the  inter- 
substance  between  these  are  found    large,  homogeneous 
nuclei,  sometimes  drawn  out  to  a  point  at  either  end  (fig. 
9b).     With  the  diminution  of  the  central  oil  globule  there 
appear  the  grape-like  clusters  of  fat  seen  in  figs.  8  a,  b, 
c.      In  fig.    8b  (a    later    stage  than  8a)    the    groups  of 
nuclei  have  increased  in  number  and  the  homogeneous 


PROTOZOA.  45 

nuclei  with  most  of  the  intersubstance  have  disappeared. 
A  difference  in  the  size  of  the  nuclei  is  apparent.  This 
difference  is  still  more  plainly  seen  in  the  later  stage  (fig. 
8c)  in  which  scarcely  a  trace  of  the  intersubstance 
remains.  Finally  the  formation  of  anisospores  takes 
place.  The  clusters  of  fat  fall  apart  into  granules  and 
each  spherical  mass  divides  into  as  many  wedge  shaped 
pieces  as  there  are  nuclei  (fig.  8d).  These  ultimately 
fall  apart  when  the  large  macrospores  (fig.  2)  and  small 
microspores  (fig.  3)  appear.  Fig.  10  is  a  mature  (usu- 
ally called  "old  vegetative")  colony  in  which  the  flagel- 
late young  are  ready  to  be  set  free  by  the  disintegration 
of  the  colony.  It  is  distinguished  from  the  young  colony 
(fig.  4)  by  its  plain  articulations. 

According  to  Haeckel  the  same  Polycyttaria  or  colonial 
Radiolaria  which  produce  anisospores  also  produce,  at 
other  times,  the  asexuaf  isospores,  so  that  it  would  seem 
that  these  two  forms  of  reproduction  alternate  with  each 
other,  and  if  so,  we  have  here  in  the  simplest  subkingdom 
of  animals  the  phenomenon  of  alternation  of  generations. 
This  variability  in  function  as  well  as  variability  in  struc- 
ture is  just  what  one  would  expect  to  find  among  organ- 
isms which  have  not  yet  learned  the  ways  of  their  more 
specialized  and  therefore  more  stable  descendants. 

MASTIGOPHORA. 

We  now  come  to  a  group  whose  peculiar  and  more  or 
less  constant  characteristic  is  the  possession  of  a  whip  or 
flagellum,  and  which  for  this  reason  is  known  by  some  as 
the  Mastigophora  and  by  others  as  the  Flagellata.  We 
have  found  the  flagellum  among  the  Rhizopoda,  Heliozoa, 
and  Radiolaria  ;  wherever,  in  fact,  there  has  been  need  for 
rapid  motion  it  seems  to  have  been  developed  as  an  adap- 
tive character.  In  the  typical  Mastigophora  it  seems  to 
have  become  fixed  in  the  organization  and  therefore  an 


46  SYNOPTIC    COLLECTION. 

inherited  character.  The  variability  of  this  organ  in  the 
intermediate  forms,  and  the  close  connection  between  the 
Heliozoa  and  Mastigophora  are  shown  in  the  extremely 
interesting  transitional  organism,  Dimorpha  mutans  Gru- 
ber,1  to  which  we  have  already  referred.  When  first 
observed  the  animal  ajppeared  to  be  an  Amoeba  radios  a 
or  a  Heliozoan,  but  suddenly  it  fell  into  a  trembling 
motion  and  a  long  whip  was  thrown  out.  PL  50,  figs,  i— 8, 
show  the  changes  undergone  in  about  two  hours.  In 
fig.  i  the  animal  is  leaving  the  Heliozoan  stage,  the  body 
is  still  spherical,  but  the  pseudopodia  are  short  and  one 
long  whip  begins  to  strike  the  water.  The  next  moment 
the  body  is  extended  lengthwise  and  becomes  egg-shaped. 
The  pseudopodia  shorten  themselves  still  more,  and  the 
Dimorpha  begins  to  swim  propelled  by  two  long  whips. 
At  times  one  of  the  whips  beats  the  water  while  the  other 
trails  behind  (fig.  2).  Suddenly  the  animal  stops  swim- 
ming and  turns  the  forward  end  of  its  body  downward 
while  the  whips  feel  about  on  the  bottom  (fig.  3).  All 
movements  cease,  the  body  becomes  spherical  and  frcia 
every  side  fine  ray-like  pseudopodia  are  thrust  out  (fig.  4). 
But  the  Dimorpha  seems  not  satisfied  with  the  spot  it  has 
chosen,  or  it  is  disturbed  in  some  other  way,  for  the  above 
described  transformation  occurs  again  (fig.  5),  and  the 
body  becomes  quite  smooth  during  its  rapid  swimming 
(fig.  6) .  The  little  sun-animal  has  transformed  itself 
into  such  a  perfect  whipped  creature  that  it  is  difficult  to 
keep  track  of  it  among  the  other  flagellate  organisms  in 
the  water.  After  swimming  about  it  comes  to  rest  again 
(fig.  7),  "thrusts  out  its  pseudopodia,  and  transforms  itself 
in  a  few  moments  into  a  Heliozoan  (fig.  8).  Fig.  9  repre- 
sents the  Dimorpha  in  its  usual  condition.  The  body  is 
pointed  at  the  posterior  end  where  the  food  elements 
are  crowded  closely  together.  Gruber.  to  whom  we  are 
indebted  for  the  above  description,  tried  various  experi- 

iZeitschr.  f.  wiss.  Zool.,  XXXVI,  1882,  p.  445. 


PROTOZOA.  47 

ments  and  found  he  was  able  to  force  the  animal  from  a 
Heliozoan  to  a  flagellate  condition  by  striking  the  sides 
of  the  dish  when,  as  if  disturbed,  the  Dimorpha  would 
develop  whips  and  swim  quickly  about. 

The  flagellate  Mastigophora  are  well  represented  by 
the  series  of  forms  shown  in  PL  51.  The  body  of  Monas 
termo  Ehr.  ?  (fig.  i,  x  950)  is  occasionally  somewhat 
amoeboid,  sending  out  short  pseudopodia-like  continua- 
tions. It  is  a  free-swimming  animal  but  may  become 
fastened  temporarily  by  a  thread-like  prolongation  of  the 
posterior  end  of  the  body  (fig.  2,  x  1200).  At  the  for- 
ward end  is  the  whip  or  flagellum,  and  on  one  side  of  its 
base  is  the  beak-like  prominence  or  lip.  Between  this  lip 
and  the  base  of  the  flagellum  is  the  mouth,  which,  how- 
ever, does  not  extend  into  an  oesophagus.  The  flagellum 
catches  the  food  and  it  is  thrown  with  a  sudden  jerk 
directly  against  the  mouth.  "If  acceptable  for  food  the 
flagellum  presses  its  base  down  upon  the  morsel,  and  at 
the  same  time  the  lip  is  thrown  back  so  as  to  disclose  the 
mouth,  and  then  bent  over  the  particle  as  it  sinks  into 
the  latter.  When  the  lip  has  obtained  a  fair  hold  upon 
the  food,  the  flagellum  withdraws  from  its  incumbent 
position,  and  returns  to  its  former  rigid,  watchful  cordi- 
tion.  The  process  of  deglutition  is  then  carried  on  by 
the  help  of  the  lip  alone,  which  expands  laterally  until  it 
completely  overlies  the  particle.  All  this  is  done- quite 
rapidly,  in  a  few  seconds;  and  then  the  food  glides 
quickly  into  the  depths  of  the  body,  and  is  enveloped  in 
a  digestive  vacuole,  whilst  the  lip  assumes  its  usual  coni- 
cal shape  and  proportions."  We  have  quoted  the  above 
from  Prof.  H.  James-Clark1  to  show  the  specialization  in 
structure  which  characterizes  this  animnl.  In  none  of 
the  Protozoa  already  described  have  we  found  an  appara- 
tus for  forcing  food  into  the  body  at  one  particular  place. 
If  this  process  were  long  continued,  it  is  not  difficult  to 

1  Mem.  Boston  Soc.  Nat.  Hist.,  I,  1866,  p.  307. 


48  SYNOPTIC    COLLECTION. 

understand  how  the  mouth,  oesophagus,  and  the  other 
tubes  and  sacs  of  the  digestive  system  originated.  After 
the  food  has  been  retained  in  the  body  for  a  time  the 
excrement  is  thrown  out  at  a  place  near  the  mouth  or 
through  the  mouth  itself,  instead  of  being  ejected  from 
any  part  of  the  body,  as  is  the  rule  with  the  Amoeba. 

Reproduction  takes  place  in  this  .genus  by  longitudinal 
fission  and  by  the  breaking  up  of  the  body  into  flagellate 
young.  The  researches  of  Messrs.  Dallinger  and  Drys- 
dale  have  shown  that  the  phenomenon  of  fission  in  these 
minute  forms  "  is  not  a  mere  division  of  undifferentiated 
sarcode  into  two  parts."  Before  separation  takes  place 
there  is  always  a  germination  of  the  anatomical  elements 
which  make  the  new  monad  complete,  while  in  many 
instances  the  fission  is  preceded  by  a  suddenly  induced 
amoeboid  condition.1 

The  young  Monosiga  globulosa  S.  K.  (PI.  51,  fig.  3)  is 
a  free-swimming  uniflagellate  form  which  bears  a  resem- 
blance to  Monas  (PL  51,  fig.  i).  In  course  of  time  it 
becomes  stationary,  as  seen  in  fig.  4.  Next,  the  stem  and 
collar  are  developed  (fig.  5  is  the  adult),  the  latter  being 
the  peculiar  characteristic  of  many  Flagellata  but  which 
is  entirely  wanting  in  the  young  Monosiga  and  in  the 
adult  Monas.  It  has  been  pointed  out  by  Kent  that  this 
collar  is  a  film  of  protoplasm  which  can  be  extended  and 
withdrawn  at  will  into  the  substance  of  the  body  in  the 
same  way  as  the  pseudopodia  of  an  Amoeba.  Combined 
with  the  flagellum  it  serves  as  a  most  efficient  trap  for 
obtaining  food.  Fig.  6  is  the  adult  of  another  species, 
Monosiga  gracilis  S.  K.,  greatly  magnified.  The  nucleus 
is  seen  near  the  central  part  of  the  body.  The  process 
of  digestion  is  shown  by  the  food  particles  colored  blue 
which  are  circulating  through  the  body.  In  this  genus 
reproduction  takes  place  both  by  longitudinal  and  by 
transverse  fission  and  also  by  the  breaking  up  of  the 
body  into  flagellate  young. 

1  Monthly  Micr.  Journ.,  XI,  1874,  p.  7. 


PROTOZOA.  49 

We  pass  naturally  from  the  solitary  Monosiga  to  the 
colonial  Codosiga  pulcherrimus  Jas.-Clk.  PI.  51,  fig.  7,  is 
the  single,  comparatively  young  zoon  which  has  broken 
away  from  its  colonial  home  and  is  a  free-moving  animal. 
During  its  young  life  it  swims  at  times  rapidly  with  its 
basal  end  extending  forward,  and  the  flagellum  following 
behind  "and  vibrating  in  rapid  undulatory  and  gyratory 
curves  as  if  it  were  the  screw  propeller  of  some  sub- 
aqueous vessel."1  Finding  a  favorable  spot  whereon  to 
settle,  the  Codosiga  secretes  a  stem  and  becomes  a  fixed 
animal  (fig.  8).  The  "body  is  surmounted  above  by  the 
high  collar.  The  dotted  lines  irt  the  drawing  indicate  the 
degree  of  the  lateral  vibratile  expansion  of  the  collar. 
From  the  middle  of  the  cone  of  the  body  extends  the 
flagellum.  Figs.  9-16  of  PI.  51  illustrate  the  process  of 
reproduction  by  fission,  the  stem  not  being  drawn.  At 
first  the  collar  bulged  as  seen  in  fig.  9.  Soon  after  this 
the  flagellum  grew  shorter  and  finally  disappeared,  while 
a  narrow  furrow  was  seen  in  the  anterior  part  of  the  body 
(fig.  10).  This  furrow  extended  downward,  while  the 
collar  became  more  cone-like  (fig.  n).  Soon  after  this 
the  collar  began  to  expand  and  the  body  was  divided 
about  half  way  to  its  base.  At  each  free  rounded  end  a 
flagellum  began  to  be  developed  which  kept  up  a  trembling 
motion  (fig.  12).  The  body  divided  mostly  to  the  base 
and  the  collar  broadened  (fig.  13).  The  process  of 
division  next  extended  into  the  collar  (fig.  14)  and  con- 
tinued, the  collar  growing  broader  and  longer  (fig.  15) 
until  finally  the  self-division  of  the  collar  and  body  was 
complete  and  extended  downward  into  the  pedicel  (fig. 
16).  A  colony  of  two  is  often  found;  sometimes  these 
increase  to  five  (fig.  17),  and  occasionally  as  many  as 
eight  are  produced.  Fig.  18  is  a  free-swimming  colony, 
Desmarella  moniliformis  S.  K.  The  early  stages  of  this 
species  have  not  been  observed,  and  therefore  in  the 

1  James-Clark,  Mem.  Boston  Soc.  Nat.  Hist.,  I,  1866,  p.  315. 


50  SYNOPTIC    COLLECTION. 

absence  of  positive  knowledge  we  can  only  reason  from 
analogy  in  regard  to  the  rightful  position  of  the  genus  in 
a  natural  classification.  In  more  specialized  animals 
such  as  certain  corals,  Polyzoa,  and  others,  the  free- 
swimming  colonies  are  derived  from  fixed  colonial  forms 
which  have  lost  their  organs  of  attachment.  It  is,  there- 
fore, probable  that  when  the  life  history  of  Desmarella  is 
known  it  will  be  found  that  the  earliest  stages  of  the 
genus  bear  structural  evidences  of  its  descent  from  a 
stationary  form.  If  such  evidences  are  not  obtained  by 
accurate  microscopical  research,  it  might  still  be  possible 
that  they  have  become  Vholly  obliterated  through  the 
action  of  the  law  of  acceleration  in  development.  The 
colony  of  Desmarella  is  never  large,  numbering  only 
from  two  to  eight  zoons. 

In  the  light  of  the  Flagellata  already  described,  the 
development  of  Proterospongia  haeckeliS.  K.  is  extremely 
interesting.  The  animal  begins  its  existence  as  a  single 
attached  uniflagellate  organism  without  a  collar  (PL  51, 
fig.  19).  Afterward  the  collar  develops,  and  in  this  stage 
the  Proterospongia  resembles  a  Monosiga.  Next  a  muci- 
laginous film  is  extended  around  the  body  below  the  col- 
lar (fig*  20).  By  binary  fission  two  zoons  are  produced 
(fig.  21).  Figs.  22  and  23  represent  small  colonies  and 
fig.  24  a  large  one  of  between  forty  and  fifty  zoons. 
Cells  migrate  from  the  surface  to  the  interior  and  become 
reproductive  in  function.  Some  of  the  zoons  in  figs.  23 
and  24  have  drawn  in  their  flagella  and  the  body  has 
assumed  an  amoeboid  appearance.  This  is  in  prepara- 
tion for  the  encysted  state  (see  fig.  24),  after  which  the 
mass  breaks  up  into  a  large  number  of  flagellate  young. 

All  the  Mastigophora  or  Flagellata  so  far  described 
belong  to  the  subclass  Flagellidia.  The  following  Dino- 
flagellidia  are  represented  by  Peridinium  and  the  Cysto- 
flagellidia  by  Noctiluca. 

The  species  Peridinium  tripos  Ehr.  (PI.  52,  fig.  i)  is 
provided  with  a  transverse  groove.  According  to  the 


PROTOZOA.  51 

observations  of  Klebs  and  Biitschli  a  second  flagellum 
lies  horizontally  in  this  groove  which  has  hitherto  been 
mistaken  for  a  girdle  of  cilia.  The  body  is  covered  with 
a  cellulose  (Bergh)  carapace  formerly  supposed  to  be 
silicious  or  chitinous,  and  its  shape  is  unique,  having 
three  horns,  two  of  which  are  in  front  and  one  behind. 
Kent l  has  pointed  out  the  isomorphic  resemblance  exist- 
ing between  the  bodies  of  the  Peridinidae  and  the  larvae 
of  certain  Echinoderms  and  Crustacea.  The  mechanical 
conditions  for  a  floating  existence  have  probably  been  the 
controlling  cause  of  this  peculiar  shape  of  the  body. 

PI.  52,  fig.  2  (P.  arcticum  Ehr.,  dorsal  view)  has  long 
arms  and  the  serrations  seen  in  fig.  i  have  here  become 
spines.  According  to  Claparede  and  Lachmann  these  are 
two  of  a  large  number  of  varieties  of  the  species  of  Cera- 
tium  tripos.  Although  these  two  forms  may  occur  in  the 
same  locality,  the  Peridinium  arcticum  Ehr.  is  found  most 
abundantly  in  the  colder,  denser  waters  of  the  arctic  seas, 
where  its  broader  and  stouter  arms  probably  assist  in 
preserving  the  equilibrium  of  the  body. 

We  come  now  to  one  of  the  members  of  the  group  of 
Mastigophora  which  has  long  been  known  on  account 
of  its  remarkable  property  of  brilliant  phosphorescence. 
The  Noctiluca  miliaris  Sur.  is  cosmopolitan,  and  to  it  are 
largely  due  the  beautiful  illuminations  of  the  sea  at  night. 
The  young  Noctiluca  (PI.  53,  figs.  1-6)  shows  specializa- 
tion in  structune  by  the  possession  of  a  whip  and  a  tenta- 
cle-like organ  near  the  mouth.  The  adult  (PI.  53,  fig.  7) 
has  a  transparent  body  in  the  form  of  a  peach  surrounded 
by  a  distinct  membrane.  The  protoplasm  radiates  from 
the  center  of  the  body,  and  spreads  itself  in  a  layer  over 
the  inner  surface  of  the  membrane  (Kent).  The  mouth 
is  at  the  bottom  of  a  depression  where  the  flagellum 
originates  (which  is  not  clearly  seen  in  the  drawing2)  and 

1  Manual  of  the  Infusoria,  I,  1880,  p.  452. 

2  See  Huxley,  Quart.  Journ.  Micr.  Sci.,  Ill,  1855,  PI.  5,  fig.  3. 


52  SYNOPTIC    COLLECTION. 

near  it  is  the  "tooth"  and  the  long  tentacle-like  organ 
which  is  transversely  striated.  The  mouth  leads  into  a 
tube  and  this  to  a  digestive  sac.1 

The  reproduction  of  the  Noctiluca  has  been  described 
in  detail  by  Cienkowski.'2  This  investigator  maintains 
that  we  have  here  two  identical  histological  cells  blending 
and,  therefore,  that  conjugation  in  the  Noctiluca  belongs 
in  the  rank  of  such  phenomena  of  blending  as  aim  at  an 
accelerated  assimilation,  and  that  it  stands  in  no  relation 
with  the  more  specialized  sexual  process  of  reproduction 
of  the  Metazoa.  This  view  may  certainly  be  questioned, 
since  the  act  of  conjugation,  upon  which,  according  to 
Cienkowski,  the  formation  of  swarmers  seems  to  be  in  a 
high  degree  dependent,  if  not  a  sexual  act,  is  most  proba- 
bly the  initiative  process  leading  towards  the  more  spe- 
cialized sexual  process  of  the  Metazoa. 

While  it  is  true  that  most  of  the  Mastigophora  have 
only  one  nucleus,  yet  this  one  is  not  probably  identical  in 
constitution  with  the  simple  nucleus  of  the  Amoeba  or 
with  the  nuclei  of  a  many  nucleated  Rhizopod,  since  con- 
jugation between  the  zoons  of  the  Mastigophora  is  the 
rule  rather  than  the  exception,  and  this  more  constant 
differentiation  in  the  process  of  reproduction  is  doubtless 
attended  with  a  differentiation  in  the  nature  of  the  repro- 
ductive organ.  Associated  with  this  specialization  of 
process  and  function  there  is  also  the  structural  differ- 
entiation of  a  primitive  digestive  system,  «and  of  a  more 
or  less  stable  body  with  its  constant  accompaniment,  in 
youth  as  well  as  in  adult  life,  of  a  locomotive  and  prehen- 
sile organ.  For  these  reasons  the  Mastigophora  (—  Flagel- 
lata)  may  be  considered  as  more  specialized  organisms 
than  the  Rhizopods.  Although  Bergh  3  has  supported  the 
opposite  view  considering  that  the  Rhizopods  have  arisen 
from  the  Flagellata,  nevertheless  the  burden  of  evidence 

1  Packard,  Zoology,  1886,  pp.  33,  34. 

2  Arch.  f.  mikr.  Anat.,  IX,  1873. 

3  Morph.  Jahrb.,  VII,  1882,  pp.  272,  273. 


PROTOZOA.  53 

seems  to  be  against  this  view  if  we  maintain  that  the 
more  elementary  organisms  came  into  existence  first  and 
gave  rise  to  the  secondary  or  more  complicated  forms. 
Surely  one  of  the  simplest  representatives  of  the  Flagel- 
lata,  the  Monas  termo,  already  described,  is  much  more 
specialized  than  the  structureless,  organless,  ever-chang- 
ing mass  of  protoplasm,  the  Protamoeba. 


INFUSORIA. 

The  cilia  or  short  hairs  that  clothe  the  cell  of  an  Infu- 
sorian,  either  partly  or  wholly,  constitute  one  of  the 
important  characters  of  this  most  specialized  group  of 
Protozoa.  We  have  seen  that  pseudopodia  and  flagella 
can  be  converted  the  one  into  the  other,  but  this  is  not 
the  case  with  pseudopodia  and  cilia.  The  latter  have 
become  permanent  and  unchanging  locomotive  organs. 
They  move  in  unison  after  the  fashion  of  paddles,  while 
the  flagellum  may  be  likened  to  a  whip. 

One  of  the  commonest  Infusorians  to  be  found  in  stag- 
nant water  and  vegetable  infusions  is  Paramoecium  cauda- 
tum  Ehr.  (PI.  54).  Although  of  comparatively  large 
size,  its  rapid  twisting  motions  make  it  difficult  to  observe 
its  many  interesting  specializations  of  structure.  The 
flagellum  which  we  have  seen  so  often  in  preceding  forms 
has  disappeared,  and  the  body  of  the  Paramoecium  is 
provided  with  cilia  which  extend  in  longitudinal  rows. 
Here  is  found  greater  differentiation  in  the  digestive  sys- 
tem, since  the  mouth  which  is  at  the  bottom  of  the  ciliated 
depression  (near  the  lower  of  the  two  outer  arrows  in  the 
left  of  the  figure)  leads  into  a  tube  that  extends  down- 
ward a  short  distance.  Food  was  given  the  Paramoecium 
in  the  form  of  partly  decomposed  indigo  obtained  from 
maceration  of  the  leaves  of  the  indigo  plant,  also  carmine 
from  dried  cochineal  insects.  The  arrows  on  the  left  of 
the  drawing  indicate  the  course  of  the  particles  of  indigo 


54  SYNOPTIC    COLLECTION. 

as  they  were  whirled  along  by  the  cilia  of  the  disc.  Many 
of  the  particles  are  seen  passing  downward  into  the  tube 
at  the  end  of  which  they  have  formed  a  pellet  that  be- 
comes surrounded  by  a  jelly-like  substance.  The  arrows 
within  the  body  show  the  definite  course  of  the  pellets  in 
the  body  cavity.  The  nourishment  having  been  separated 
from  the  food,  the  excrement  is  ejected  at  the  swelling 
which  rises  temporarily  on  the  ventral  side  of  the  poste- 
rior part  of  the  body,  as  seen  on  the  left  of  the  drawing. 
The  contractile  vesicle  according  to  Kent  is  normally 
spherical,  as  represented  in  the  posterior  part  of  the 
body,  but  under  pressure  it  assumes  the  condition  seen 
in  the  anterior  portion  of  the  body  extending  outward  in 
the  form  of  ray-like  continuations.  The  nucleus,  colored 
yellow  in  the  drawing,  is  the  long  tubular  organ  with 
three  enlargements  just  in  front  of  the  posterior  spherical 
contractile  vesicle.  E.  Ray  Lankester1  has  shown  in 
Paramoedum  aurelia  Mull.2  a  marked  differentiation  of  the 
protoplasm  into  two  well  denned  parts.  The  outer  por- 
tion is  bounded  by  a  cuticle  that  is  pierced  by  holes 
through  which  pass  the  cilia.  Just  under  the  cuticle  are 
little  sacs  or  tricocysts,  each  one  containing  a  thread 
which  can  be  thrown  out,  and  which  is  helpful  as  a  defen- 
sive and  probably  as  an  offensive  organ.  Attached  to 
one  side  of  the  nucleus  is  the  apparently  small  nucleus, 
the  paranucleus,3  which  probably  arises  from  the  nucleus. 
The  investigations  of  Balbiani  and  others  have  shown 
that  the  reproductive  phenomena  of  Paramoecium  and  the 
Infusoria  generally  are  more  complicated  than  those  of 
the  Rhizopods  or  the  Flagellata.  Temporary  conjuga- 
tion takes  place  between  the  zoons  of  Paramoecium  and 

1  Encycl.  Brit.,  ed.  9,  XIX,  1885. 

2  The  Paramoecium  caudatum  of  Ehrenberg  is  probably  a  variety 
of  the  P.  aurelia  of  M tiller. 

3  The  paranuclei  are  sometimes  called  nucleoli.  but  objectionably, 
since  the  paranucleus>  has  nothing  to  do  with  the  nucleolus  of  a 
typical  cell  (E.  Ray  Lankester,  Encycl.  Brit.,  ed.  9,  XIX,  1885). 


PROTOZOA.  55 

may  last  five  or  six  days  or  even  longer.  This  union 
brings  about  important  changes,  the  nucleus  is  broken 
up,  the  paranuclei  divide,  and  protoplasm  may  be  inter- 
changed as  wejl  as  paranuclei.  The  two  zoons  then  sep- 
arate and  a  reconstruction  of  the  parts  takes  place  with 
rejuvenescence  of  the  organs  followed  by  fission.1 

While  Paramoecium  is  a  free-swimming  single  form  in 
youth  and  adult  life,  Stentor  polymorphus  Mull.  (PI.  55, 
figs.  1-3)  is  sometimes  a  single  swimmer  when  young 
and  often  a  stationary  and  colonial  form  when  full  grown. 
The  little  embryo  of  Stentor  (fig.  i)  is  nearly  spherical  in 
shape  (the  ground  form  of  most  Protozoa).  Its  cilia, 
even  when  within  the  body  of  the  parent,  are  developed, 
but  it  possesses  neither  a  mouth  nor  an  esophageal  tube. 
In  time,  however,  these  appear  (fig.  2)  ;  the  rounded 
body  becomes  trumpet-shaped  and  is  often  attached  to 
some  object.  The  Stentor  then  secretes  a  mucilaginous 
sheath  about  the  posterior  tubular  portion  of  its  graceful 
body  (fig.  3).  The  upper  anterior  expansion  of  the 
trumpet  has  the  delicate  wreath  of  cilia  and  the  large 
cilia  near  the  mouth  describe  a  spiral.  The  mouth  ex- 
tends into  a  spiral  tube. 

The  protoplasm  of  Stentor  has  become  differentiated  to 
form  a  layer  of  thread-like  fibrillae  which  extends  from 
the  anterior  to  the  posterior  end  of  the  body  and  is 
extremely  elastic.  Another  set  of  these  fibrillae  surrounds 
the  ciliated  disc  and  helps  to  close  this  region  when  the 
Stentor  is  contracted.  This  differentiated  layer  of  elastic 
fibrillae  is  probably  the  initial  form  of  the  muscular  sys- 
tem of  the  more  specialized  animals.  The  long  beaded 
nucleus  is  seen  at  the  right  of  PI.  55,  fig.  3.  Unlike  most 

1  According  to  Eigenmann  (Bull.  U.  S.  Fish  Commission,  XII, 
1892),  the  ciliate  Infusoria  have  two  nuclei,  the  macronucleus  and 
the  micronucleus,  the  former  of  which  is  probably  represented  by 
the  yolk  nucleus  of  the  Metazoa.  This  author  gives  a  diagram 
showing  the  maturation,  conjugation,  and  segmentation  of  Protozoa 
and  Metazoa. 


56  SYNOPTIC    COLLECTION. 

Protozoa  the  Stentor  divides  obliquely  instead  of  trans- 
versely or  longitudinally.  This  is  in  accordance  with  the 
spiral  structure  of  the  Infusoria.  Just  above  the  mucilag- 
inous sheath  the  lateral  line  of  cilia  is  seen  to  curve  spi- 
rally ;  this  marks  the  spot  where  a  future  zoon  is  to  arise 
by  fission.  The  newly  formed  zoon  sometimes  remains 
with  the  parent,  producing  a  small  colony. 

Gruber l  ascertained  by  experiment  that  division  of 
Stentor  took  place  in  most  cases  at  intervals  of  two  days, 
that  daughter  zoons  divided  into  granddaughters  in  the 
second  day  after  their  separation,  and  granddaughters  in 
another  two  days  into  great  granddaughters,  and  so  on. 
In  42  out  of  56  cases  division  took  place  on  the  second 
day  after  the  preceding  one.  This  mode  of  reproduction 
is  not  the  only  one  peculiar  to  Stentor.  A  further  differen- 
tiation in  the  process  of  fission  is  observable.  The 
nucleus  develops  germs  or  embryos  which,  becoming 
detached  from  it,  leave  the  body  of  the  parent  and  swim 
freely  about.  Such  embryos  are  represented  by  figs,  i 
and  2  in  PI.  55. 

We  will  now  pass  to  a  fixed  colonial  form  of  the  Infu- 
soria. The  student  of  nature  may  find  keen  enjoyment  in 
the  study  of  the  beautiful  bell  Vorticellidae.  These  Pro- 
tozoa are  characterized  by  marked  specializations  of  struc- 
ture. The  protoplasm  of  which  the  bell-shaped  body  is 
made  has  become  differentiated  into  three  parts,  the  cu- 
ticle, ectosarc,  and  endosarc.  Furthermore,  the  ectosarc 
has  undergone  a  change  whereby  the  outer  portion  has 
become  converted  into  a  muscular  layer  which,  according 
to  some  authors,  extends  into  the  stem,  forming  the  highly 
contractile  spiral  axis.  The  digestive  system  has  become 
developed  so  that  there  is  not  only  a  mouth  opening  but 
a  distinct  tube-esophagus  leading  downward  into  the 
body.  At  the  mouth  opening  this  tube  flares,  and  the 
enlargement  is  often  called  the  vestibule,  while  the  con- 
fer, naturforsch.  Gesellsch.  Freiburg  i.  B.,  I,  1886,  Heft  2. 
Engl.  transl.,  Ann.  and  Mag.  Nat.  Hist.,  (5),  XVII,  1886,  p.  473. 


PROTOZOA.  57 

tracted  portion  of  the  tube  beyond  is  the  esophagus 
proper.  As  yet  the  digestive  system  is  not  complete, 
there  being  no  separate  opening  or  anus  on  the  surface 
for  the  exit  of  waste  matter.  If  the  Vorticella  is  given 
carmine  or  indigo,  the  way  the  food  is  caught  by  the 
cilia  (which  are  borne  on  the  thickened  rim  or  peristome 
surrounding  the  disc  of  the  bell)  and  its  circulation 
through  the  ciliated  vestibule  and  esophagus  and  through 
the  endosarc  of  the  body  to  its  exit  at  the  mouth,  can  all 
be  observed  with  the  microscope.  With  the  differentia- 
tion of  the  muscular  and  digestive  systems  there  is  a 
greater  specialization  in  the  reproductive  system  and  in 
the  processes  which  lead  to  increase.  PI.  56,  figs.  1-29, 
taken  from  Everts,1  illustrate  the  process  of  reproduction 
through  longitudinal  fission,  and  figs.  30-34,  after  Greef,2 
the  process  through  the  conjugative  act.  Beginning  with 
the  little  ball  (fig.  i)  which  issues  from  the  cyst,  we  find 
it  a  tiny  mass  of  protoplasm  showing  no  differentiation. 
It  agrees  structurally  at  this  time  with  a  cytode,  since  no 
cell  wall  is  discovered,  and  it  is  not  until  the  cilia  are 
developed  that  it  becomes  a  cell  with  a  nucleus.  A  vac- 
uole  appears  (fig.  2),  next  a  swelling  (fig.  3),  and  a  wreath 
of  cilia  (fig.  4).  The  form  changes  and  an  organism 
appears  which  is  likened  by  Everts  to  the  Trichodina 
grandinella  described  by  Ehrenberg. 

This  Trichodina  (fig.  5)  continues  to  grow  (figs.  6-9) 
until  transverse  constriction  takes  place  with  a  separation 
into  two  Trichodinas  (fig.  10).  Then  the  body  lengthens 
(figs,  n,  12)  with  the  formation  of  the  peristome  (fig.  13), 
after  which  the  stem  is  secreted  (figs.  14-17).  Fig.  iya 
represents  a  stemmed  Vorticella  much  enlarged.  This 
form  contracts  (fig.  18),  the  body  broadens  (fig.  19),  and 
the  nucleus  ta*kes  a  position  at  right  angk  s  to  the  stem. 
A  constriction  takes  place  (fig.  20)  which  increases  (fig. 
21)  until  the.  division  is  complete  (fig.  22).  A  wreath  of 

•Zeitschr.  f.  wiss.  Zool.,  XXIII,  1873. 
2  Arch.  f.  Naturg.,  XXXVI,  I,  1870. 


58  SYNOPTIC    COLLECTION. 

cilia  next  appears  at  the  posterior  end  of  the  body  of  one 
of  the  zoons  (fig.  23),  the  forward  end  contracts,  the  disc 
and  cilia  are  drawn  in  (fig.  24),  and  finally  by  strong 
efforts  the  zoon  frees  itself  (fig.  25).  The  remaining 
zoon  afterward  becomes  free  in  a  similar  manner.  The 
movements  of  the  free  Vorticella  are  lively  for  a  time, 
then  it  becomes  quiet,  takes  on  a  spherical  form  (figs.  26, 
27),  the  wreath  disappears  and  the  nucleus  divides  (fig. 
28).  The  shrunken  cyst  covering  is  seen  in  fig.  29  with 
seven  balls  within.  This  completes  the  life  cycle.  This 
species  also  increases  through  conjugation,  as  has  been 
stated.  A  smaller  zoon,  the  microgonidium,  approaches  a 
larger  stemmed  zoon,  the  macrogonidium  (fig.  30).  The 
basal  part  becomes  drawn  in  to  form  the  sucker  by  means 
of  which  the  small  zoon  attaches  itself  to  the  side  of  the 
larger  one  (fig.  31).  When  this  is  done,  the  conical  base 
is  stretched  out  again,  whereby  a  boring  organ  is  pro- 
duced, and  the  body  of  the  small  Vorticella  becomes  a 
mere  lump  (fig.  32).  Gradually  the  contents  of  the  body 
pass  wholly  into  the  larger  zoon,  leaving  only  a  sac-like 
skin  (fig.  33).  The  bristles  on  this  sac  may  be  the  wrin- 
kles of  the  ring-like  cuticle.  Finally  the  sac-like  skin  is 
thrown  off  (fig.  34),  and  the  two  animals  are  fused 
together  indistinguishably.  It  would  seem  that  here  the 
whole  body  of  the  zoon  corresponds  to  the  ovum  and  the 
spermatozoon,  and  if  so,  We  have  as  the  result  of  their 
union  a  fertilized  egg.  Much  difference  of  opinion  exists, 
however,  in  regard  to  the  real  significance  of  the  act  of 
conjugation.  But  whether  this  act  is  a  sexual  or  an  asex- 
ual one,  it  can  be  said  with  certainty  that  the  process  is 
far  more  specialized  than  the  apparently  accidental  fusion 
of  the  Rhizopods.  Furthermore,  it. is  rational  to  suppose, 
as  before  stated,  that  this  process  is  at  least  the  initiatory 
leading  to  the  complicated  reproductive  phenomena  of  the 
specialized  Metazoa. l 

1  For  a  discussion  of   this   subject,  see  Calkins,  The  Protozoa, 
1901,  chapter  VII. 


PROTOZOA.  59 

It  is  interesting  to  note  that  in  one  species  of  this 
genus,  Vorticella  umbellaria  C.  &  L.,  there  are  nemato- 
cysts  or  thread  cells  which  are  more  effective  weapons 
than  the  tricocysts.  Each  of  these  cells  contains  a 
spirally  wound  thread,  like  the  thread  cells  of  the  more 
specialized  Coelentera  soon  to  be  described. 

The  compound  colonial  form,  Zoothamnium  alternans 
C.  &  L.  (PI.  57),  is,  according  to  Kent,  one  of  the  most 
remarkable  instances  of  polymorphism  among  the  Infuso- 
ria. In  this  genus  there  are  three  differentiated  forms  of 
zoons.  PI.  57  shows  two  of  these  forms.  The  large 
size  of  the  macrogonidia  in  this  species  is  unusual. 


INFUSORIA. — TENTACULIFERA. 

The  Tentaculifera  are  represented  in  the  Collection  by 
the  Podophrya  gemmipara  Hertwig  (PL  58,  figs.  1-4, 
a-e).  By  the  possession  of  cilia,  the  young  form  (fig.  i) 
shows  its  probable  relationship  with  the  ciliate  Infusoria. 
In  the  course  of  development  the  cilia  disappear.  Kent 
observed,  however,  in  specimens  obtained  from  North 
Wales  in  1 88 1,  that  the  embryos  were  provided  with 
short  tentacles  either  in  addition  to  or  in  place  of  a  more 
or  less  conspicuously  developed  ciliary  covering.  Fig.  2 
is  a  young  form  showing  the  origin  of  the  stem.  The 
adult  (fig.  3)  is  much  more  differentiated.  The  food- 
catching  organs  or  tentacles  have  increased  in  number. 
Nutting1  has  given  figures  of  another  species  of  Podo- 
phrya (probably  P.  compressa)  showing  how  the  young 
embryo  after  becoming  attached,  develops  a  few  tentacles 
at  first,  which  increase  in  number  with  the  growth  of  the 
animal.  Besides  the  tentacles  there  are  sucking  tubes 
which  broaden  out  at  the  end  after  the  fashion  of  a 
sucker  (see  fig.  3).  The  prey  is  caught  by  the  tentacles 

iAmer.  Nat.,  XXII,  1888. 


60  SYNOPTIC    COLLECTION. 

and  afterward  sucked  into  the  body  of  the  Podophrya  by 
means  of  the  sucking  tube,  though  the  process  is  not  well 
understood. 

Propagation  takes  place  by  the  formation  of  buds  or 
embryos  from  the  oral  surface.  Eight  of  these  buds  are 
seen  in  PI.  58,  fig.  4.  The  nucleus  in  the  young  forms  is 
comparatively  simple,  but  in  the  large,  old  specimens  it 
has  an  extraordinarily  complicated  structure.  This 
increase  in  complexity  is  finely  shown  in  figs.  a-e. 
Fig.  a  is  a  young  Podophrya  with  a  simple  horseshoe 
nucleus  ;  in  fig.  b  the  nucleus  has  changed  its  form,  and 
in  fig.  c  it  has  become  forked.  Fig.  d  shows  four  embryos 
with  the  branches  of  the  nucleus  extending  towards 
them,  and  in  fig.  e  they  have  penetrated  the  embryos. 

In  this  sketch  of  the  Protozoa  we  have  attempted  to 
point  out  some  of  the  many  differentiations  whereby  a 
structureless  mass  of  protoplasm,  like  Protamoeba,  may 
become  a  specialized  organism  like  an  Infusorian. 


MESOZOA. 

The  division  of  animals  known  as  the  Mesozoa  holds 
middle  ground  between  the  Protozoa  and  the  Metazoa, 
and  is  of  great  importance  from  a  phylogenetic  point  of 
view,  as  will  be  seen  hereafter  when  the  development  of 
the  egg  of  a  Metazoan  is  traced. 

The  Mesozoa  are  represented  in  the  collection  by 
Volvox  globator  L.  No  drawing  can  reproduce  the  beauty 
of  the  living  Volvox.  A  tiny  ball  of  vivid  green,  it 
revolves  through  the  water  with  graceful  and  rapid  mo- 
tions, offering  a  puzzle  to  both  the  botanist  and  the 
zoologist.  Although  claimed  as  a  plant  by  a  number  of 
botanists,  its  morphological  relations  to  animal  forms  and 
the  history  of  its  development  lead  many  zoologists  to 
place  it  among  animals. 

It  seems    probable  that  Volvox   has  arisen  from   the 


MESOZOA.  61 

Protozoa  Flagellata,  among  which  it  is  placed  by 
Biitschli,  who,  nevertheless,  says  that  strictly  speaking 
the  genus  does  not  belong  here,  since  the  so-called  colo- 
nies are  in  reality  many-celled  individuals.1 

We  have  in  Volvox  an  organism  of  many  cells  which 
are  arranged  in  one  layer  around  a  central  cavity.  This 
cavity  is  hollow  in  so  far  as  it  is  destitute  of  cells,  though 
it  is  filled  with  a  gelatinous  cellulose  substance  which  is 
secreted  by  the  cells  and  in  the  periphery  of  which  they 
lie  embedded,  connected  by  delicate  threads  of  proto- 
plasm. 

It  has  already  been  shown  that  many  adult  Protozoa 
represent  the  simple  unfertilized  egg,  and  that  probably 
some  of  the  most  specialized  members  of  this  branch, 
such  as  Vorticella,  reach  in  their  development  the  condi- 
tion of  the  fertilized  egg.  If,  now,  this  egg  were  to 
divide  and  the  products  of  division  remain  together  and 
arrange  themselves  in  a  layer  around  a  central  cavity, 
then  we  should  have  the  next  stage  of  development  of 
the  fertilized  egg,  known  as  the  blastula,  which  is  well 
represented  by  the  adult  Volvox. 

In  Volvox  the  peripheral  layer  is  made  of  flagellate 
motor  and  feeding  cells  called  somatic  cells  (PL  59,  fig. 
i).  There  may  be  12,000  of  these  cells  in  an  adult 
and  each  one  has  two  long  whips  which  pierce  the  outer 
wall  surrounding  the  cells.  A  few  of  these  somatic  cells 
which  migrate  from  the  surface  and  are  just  inside  of  this 
peripheral  layer  have  the  power  of  dividing  or  of  asexual 
reproduction,  and  are  known  as  parthenogonidia  (PL  59, 
fig.  2  a-e,  illustrating  the  process  of  divisio'n) .  These 
parthenogonidia  give  rise  to  asexual  adults  (fig.  3)  that 
often  contain  eight  smaller  Volvoces  which  revolve  within 
the  parent,  and  each  of  these  in  turn  contains  eight  more, 
so  that  three  generations  are  represented  as  seen  in  fig. 
3.  When  the  parent  capsule  is  ruptured,  the  eight  smaller 

1Bronn's  Thierreich,  II,  1883,  p.  775. 


62  SYNOPTIC    COLLECTION. 

spheres  leave  the  parent  one  by  one,  rotating  swiftly 
through  the  water. 

After  asexual  reproduction  has  continued  for  some 
time,  cells  which  are  apparently  parthenogonidia  at  first 
become  biflagellate  male  cells  or  microgonidia  (fig.  4) . 
and  large,  unflagellate  female  cells  or  macrogonidia ; 
one  of  these  macrogonidia  (fig.  5)  is  being  fertilized  by 
the  microgonidia.  This  process  of  fertilization  is  similar 
to  that  of  specialized  plants  and  animals ;  after  fertiliza- 
tion, cleavage  takes  place  and  both  somatic  cells  and  par- 
thenogonidia are  formed  before  the  embryo  leaves  the 
parent.  After  this,  the  young  develops  into  a  sexual 
adult  (fig.  6).  In  this  figure,  a  is  a  male  cell  seen  from 
above ;  a2  the  same  from  the  side ;  a8  with  the  micro- 
gonidia separated  ;  a4  with  only  a  few  microgonidia  ;  the 
others  having  escaped  are  moving  about  in  the  central 
cavity.  Fig.  6  b,  is  a  female  cell ;  b2  the  same  with 
vacuoles  in  the  inside  ;  in  b8  the  microgonidia  have  fast- 
ened themselves  on  the  gelatinous  covering  of  the  female 
cell ;  sometimes  three  penetrate  the  covering  and  bore 
into  the  interior,  when  a  fertilized  egg  results,  which  is 
the  sexual  method  of  reproduction  in  Volvox. 

The  extremely  interesting  observation  of  Ryder1  on 
Volvox  minor  shows,  that,  in  spite  of  its  nearly  spherical 
form,  there  is  a  polar  differentiation  of  the  body  with  the 
specialization  of  possible  sense  organs  at  the  anterior  pole. 
According  to  this  investigator  the  anterior  pole  of  the 
blastula  is  always  directed  forward  when  the  animal  is  in 
motion,  and  therefore  it  is  this  pole  which  is  brought  into 
the  most  dangerous  position.  Now,  it  is  instructive  to 
note  that  the  peculiar  organs  known  as  "  eye-spots  "  are 
developed  much  more  at  this  pole  than  elsewhere,  beingr 
in  fact,  so  slightly  developed  at  the  posterior  pole,  where 
there  is  little  use  for  them,  as  to  be  nearly  absent.  There- 


1  Amer.  Nat.,  XXIII,  1889,  p.  218-221  ;  also  Proc.  Acad.  Nat. 
Sci.  Phila.,  May,  1889,  p.  138-140. 


METAZOA  -  PORIFERA. 


fore  it  is  plain,  says  Ryder,  that  if  these  organs  are  visual 
or  sensitive  to  light  or  any  other  natural  agent,  they  are 
best  developed  in  just  the  position  in  which  they  are  of 
the  most  service  to  the  organism. 


METAZOA. 
PORIFERA. 

Section  i  (erect  part). 

Great  advances  have  been  made  in  the  direction  of  a 
natural  classification  of  the  Porifera  since  1872,  but 
nevertheless  naturalists  still  differ  not  only  in  regard  to 
the  systematic  position  of  these  animals,  but  also  in 
respect  to  their  anatomical  structure.1 

They  are  considered  as  members  of  the  next  more  spe- 
cialized subkingdom,  the  Coelentera,  by  Haeckel,  Leuck- 
art,  Marshall,  Polejaeff,  Schulze,  R.  von  Lendenfeld,2 
and  Ganin.  Marshall3  even  goes  so  far  as  to  regard  them 
as  reduced  members  of  this  group,  finding  evidences,  as 
he  thinks,  of  the  former  existence  of  tentacles,  thread 

1  Dr.  R.  von  Lendenfeld  has  given  a  clear  and  an  extremely  inter- 
esting history  of  our  knowledge  of  sponges  in  the  Introduction  to 
his  Monograph  of  the  Australian  Sponges,  Proc.  Linn.   Soc.  New 
South  Wales,  IX,  part   i,  1884.     For  the  most  complete  bibliogra- 
phy on  the  subject,  see  Rauff's  great  work  on  Palaeospongiologie, 
Palaeontographica,  XL,  i893~'94. 

2  According  to  this  author  the  Metazoa  are  naturally  divided  into 
two  groups  or  grades  ;  the  Coelentera  with  a  simple  undivided  body 
cavity,  all   the  parts  of  which   are  in  direct  connection  with  one 
another  ;  and  the  Coelomata,  which  have  two  distinct  and  entirely 
separated  body  cavities,  —  a  gastral  and  a  perigastric  cavity.     The 
sponges,  according  to  this  author,  have  a  simple  and  continuous 
body  cavity,  so  that  they  are  regarded  by  him  as  Coelentera  (Proc. 
Zool.  Soc.  London,  1886,  p.  565). 

3  Zeitschr.  f.  wiss.  Zool.,  XXXVII,  1882,  p.  246.     Jena.  Zeitschr., 
XVIII,  1885.     See  Ann.  and  Mag.  Nat.  Hist.,  (5),  XVI,  1885. 


64  SYNOPTIC    COLLECTION. 

cells,  and  mesenteric  pouches.  This  would  place  sponges 
after  the  Hydrozoa  and  Anthozoa  in  a  natural  classifica- 
tion, but  the  views  of  Marshall  have  not  been  established.1 
Biitschli  and  Sollas  maintain  that  sponges  belong  to 
an  independent  phylum,  and  give  it  the  name  of  Parazoa.2 

Owing  to  certain  marked  structural  characters  we  have 
considered  the  group  as  belonging  to  the  Metazoa,  but 
as  an  independent  and  primitive  group  of  this  phylum 
having  more  or  less  remote  ancestral  forms  among"  the 
Protozoa.  At  the  same  time  it  must  be  borne  in  mind  that 
the  primitive  characters  are  most  plainly  seen  before  the 
sponge  becomes  a  sessile  animal,  and  that  after  fixation 
takes  place,  certain  adaptive  characteristics  and  evidences 
of  reduction  appear.  It  would  seem  as  if  the  Porifera 
and  Coelentera,  as  descendants,  speaking  broadly,  of  the 
Protozoa  and  Mesozoa,  traveled  along  similar  roads  for  a 
short  distance  till  the  sedentary  habits  of  the  former  and 
the  free-swimming,  active  life  of  most  of  the  latter  caused 
a  divergence  of  the  roads. 

The  processes  by  which  the  Metazoa  have  arisen  from 
the  Protozoa  through  the  Mesozoa  have  not  been  deter- 
mined with  certainty.  The  two  leading  views  in  regard 
to  the  subject  are  those  of  Haeckel  and  Metschnikoff. 
According  to  the  gastraea  theory  of  Haeckel  the  fertilized 
egg  of  a  Metazoan,  a  sponge  for  example,  arises  from  an 
unnucleated  mass  of  protoplasm  comparable  with  the 
Monera  of  the  Protozoa.  Becoming  nucleated  and  fer- 
tilized, it  may  be  compared  with  the  adults  of  the  most 
specialized  Protozoa.  This  egg  becomes  segmented, 
thereby  forming  many  similar  but  still  united  cells.  These 
resemble  remotely  a  mulberry,  so  that  the  egg  at  this 
stage  is  known  as  the  morula.  The  cells  arrange  them- 
selves about  a  central  cavity  filled,  with  fluid,  and  this 
stage  is  the  blastula.  Next  the  cells  at  one  pole  of  the 

1  See  "  The  Relationships  of  the  Porifera,"  Vosmaer,  Ann.  and 
Mag.  Nat.  Hist.,  (5),  XIX,  1887,  p.  249. 

2  Reasons  for  this  classification  are  given  in  the  Rep.  Chall.  Exp., 
Zool.,  XXV,  1888,  p.  xcii. 


METAZOA PORIFERA.  65 

blastula  become  differentiated  and  turn  inward  or  become 
invaginated,  and  the  embryo  possesses  two  layers  (the 
outer  layer  or  ectoderm  and  the  inner  layer  or  endoderm), 
a  gastral  cavity  or  archenteron,  with  an  opening,  the  blas- 
topore.  As  the  process  of  digestion  was  supposed  to  go 
on  in  the  gastral  cavity,  the  embryo  at  this  stage  was 
called  the  gastrula. 

It  will  be  noticed,  that,  according  to  this  theory,  the 
invaginated  gastrula  represents  a  primitive  stage  in  the 
development,  arising  directly  from  the  blastula ;  also  that 
the  archenteron  and  blastopore  are  primitive  and  not 
secondarily  acquired  characters.  Furthermore,  the  proc- 
ess of  invagination,  by  which  these  conditions  have  been 
brought  about]  must  of  course,  according  to  this  theory, 
be  a  primitive  process.  Haeckel  maintains  that  the  proc- 
ess of  delamination  or  the  cross  division  of  cells,  to  be 
spoken  of  hereafter,  is  a  modification  of  invagination,  but 
does  not  show  how  the  one  is  derived  from  the  other. 

Extended  observations  on  sponges  and  Coelentera 
proved  that  the  occurrence  of  the  invaginated  gastrula 
was  exceptional  instead  of  normal,  as  would  be  expected 
in  these,  the  simplest  and  most  generalized  groups.  In 
Ascetta  primordialis,  one  of  the  simplest  calcareous 
sponges,  and  in  the  silicious  and  horny  sponges,  in  the 
Hydrozoa  and  Anthozoa,  the  stage  following  the  blastula 
is  not,  as  a  rule,  an  invaginated  gastrula  but  something 
quite  different.  It  is  a  solid,  mouthless  embryo,  consist- 
ing of  one  layer  of  cells  on  the  periphery  and  a  mass  of 
cells  in  the  interior. 

The  parenchymella  theory  of  Metschnikoff  throws  light 
on  the  origin  of  this  stage  of  development.  The  blastula, 
according  to  this  author,  is  converted  into  the  solid  em- 
bryo or  parenchymella1  by  the  process  of  immigration  of 
cells  from  the  surface  (such  as  was  seen  in  Proterospongia 

1  We  use  parenchymella  (Metschnikoff)  instead  of  planula  (Lan- 
kester)  because  the  theory  of  Metschnikoff  is  given  the  preference 
to  that  of  Lankester.  (See  McMurrich,  Biol.  Lect.  Mar.  Biol.  Lab.. 
Wood's  Hole,  1891.) 


66  SYNOPTIC    COLLECTION. 

and  Volvox)  and  also  by  the  delamination  of  the  inner 
ends  of  the  ectoderm  cells.  The  former  process  results 
from  the  longitudinal  division  of  the  cells,  the  latter  from 
cross  division.  In  Proterospongia  and  Volvox  the  migrat- 
ing cells  become  reproductive,  but  with  this  differentia- 
tion in  function  it  is  not  difficult  to  conceive  that  other 
cells  might  become  digestive  and  pass  to  the  interior, 
leaving  the  Ipcomotor  whipped  cells  on  the  surface. 

The  fact  now  demonstrated,  that  digestion  in  many  of 
the  more  generalized  Metazoa  is  intra-cellular,  or  carried 
on  within  the  cells,  and  not  in  a  stomach  or  archenteron, 
strengthens  the  theory  of  Metschnikoff.  •  In  time  the  cells 
within  the  solid  embryo  arrange  themselves  in  a  layer  to 
form  the  endoderm.  Later  an  opening  breaks  through 
the  two  layers,  endoderm  and  ectoderm.  The  resultant 
form  is  similar  in  appearance  to  the  invaginated  gastrula, 
but  in  this  case  it  is  clear  that  the  endoderm  is  not  formed 
as  a  bag-shaped  invagination  with  a  terminal  opening. 

The  parenchymella  is  in  reality  the  primitive  condition, 
arising  from  the  blastula,  and  the  gastrula-like  stage  is 
acquired  later. 

It  is  not  difficult  to  see  how  the  process  of  immigration 
might  apparently  give  rise  to  invagination  in  certain  cases, 
since  if  the  cells  migrated  en  masse  from  one  pole  of  the 
blastula  instead  of  individually  from  all  points  of  the  sur- 
face, a  form  would  appear  resembling  an  invaginated 
gastrula.  The  formation  of  the  parenchymella  and  the 
resultant  gastrula-like  embryo  is  the  normal  development 
of  most  of  the  Porifera  and  Coelentera,  the  invaginated 
gastrula  occurring  rarely,  as  for  example  in  Sycandra1 

1  Dr.  Otto  Maas  (Zoologische  Jahrbiicher,  Anat,  VII,  Heft  2, 
1893)  maintains  that  the  invagination  of  the  "ciliated"  cells  in 
Sycandra  has  nothing  to  do  with  the  process  of  gastrulation,  the 
two  layered  embryo  being  already  formed,  according  to  this  author, 
before  the  occurrence  of  this  invagination.  A  "  fundamental  simi- 
larity "  Dr.  Maas  finds  between  the  development  of  the  calcareous 
and  horny  sponges,  and  he  thinks  that  the  apparent  exceptions  to 
the  rule  (Sycandra,  Oscarella,  etc.)  will  be  found  to  conform  to  it  on 
further  study. 


METAZOA PORIFERA.  67 

among  the  most  specialized  calcareous  sponges  and  Ha- 
lisarca  (=Oscarella)  among  the  silicious  group.  Up  to 
the  time  of  the  formation  of  the  gastrula-like  embryo  the 
development  of  the  sponge  is  parallel  and  similar  to  that 
of  the  Coelentera.  After  the  gastrula-like  stage,  how- 
ever, the  transformations  that  the  young  sponge  goes 
through  are  peculiar  to  the  Porifera.  These  stages  end 
in  the  formation  of  an  oval  form  with  a  girdle  of  larger 
cells  and  a  circlet  of  cilia  around  what  was  the  opening 
of  the  gastrula-like  embryo,  but  which  has  been  plugged 
up  by  the  growth  of  cells  in  the  interior.  This  larva  is 
collared  ;  it  is  the  typical  Poriferan  form  and  when  one 
finds  it  he  knows  that  he  is  looking  at  the  young  of  a 
sponge.  This  little  active  creature  is  not  guided  by  its 
intelligence  in  the  search  for  food  nor  by  any  particular 
instinct.  The  tides  and  currents  carry  it  (since  its  own 
power  of  swimming  is  not  very  effective),  and  where 
they  flow  there  is  always  food  of  the  right  sort  in  abun- 
dance. If  the  little  larva  floats  out  of  the  proper  region 
it  would  fasten  itself  probably  to  any  sufficiently  smooth, 
hard  substance,  and  either  lead  a  half-starved  abbrevi- 
ated existence,  or  meet  with  an  untimely  death  choked  by 
muddy  sediments  or  killed  by  some  other  equally  effective 
agency.  When  about  to  settle,  the  collar  spreads  itself 
out  by  growth,  forming  the  base,  and  by  closely  fitting 
itself  to  the  surface  excludes  the  water  and  air,  thus  fas- 
tening the  body  by  the  weight  of  these  elements  to  "its 
selected  spot  as  a  boy  fastens  a  sucking  disk  of  wet  leather 
to  a  stone. 

The  cavity  which  appears  in  the  body  after  this  stage 
has  no  external  opening  ;  the  latter  breaks  through  at 
the  end  opposite  the  plugged  up  opening  of  the  gastrula- 
like  embryo.  The  cells  of  its  walls  have  flagella  and 
collars.  These  organs  appear  at  different  times,  and 
on  different  parts  of  the  body,  but  they  become  perma- 
nent in  the  interior  of  the  ampullae  or  little  sacs  after 
this  stage  and  are  not  found,  as  a  rule,  on  the  membranes 
of  other  parts  or  on  the  exterior. 


68  SYNOPTIC    COLLECTION. 

The  primitive  and  most  generalized  Porifera  must  be 
those  sponges  that  in  their  adult  form  and  characters 
most  nearly  approach  the  gastrula-like  embryo.  It  will 
be  seen  that  such  sponges  are  the  Calcarea  or  the  group 
of  calcareous  sponges  next  to  be  described. 


CALCAREA. 

It  cannot  be  doubted  that  a  form  existed  in  the  past 
(if  it  is  not  living  at  the  present  time)  which  possessed 
the  simple  structure  of  the  generalized  Calcarea,  but 
which  was  without  a  skeleton  of  any  kind  and  also  with- 
out the  power  of  taking  up  foreign  matter  to  make  one. 
Such  a  sponge  would  be  a  primitive  one,  and  its  develop- 
ment would  throw  much  light  on  the  origin  and  classifi- 
cation of  the  Porifera.  Until  this  gap  is  filled  we  must 
begin  with  Prophysema  primordiale  Hkl.  (PI.  60).  *  Al- 
though this  sponge  never  develops  a  skeleton,  yet  it  pos- 
sesses the  capacity,  exhibited  by  a  few  other  sponges  and 
by  some  Protozoa,  of  taking  up  foreign  substances  (in 
this  case  both  silicious  and  calcareous  spicules)  and  of 
making  a  false  skeleton  sufficient  for  the  support  of  its 
own  body. 

Prophysema  is  a  simple  attached  tube  with  one  open- 
ing, and  with  the  body  cavity  lined  with  flagellate  cells. 


form  was  previously  described  by  Haeckel  as  Haliphysema 
primordiale  Hkl.  (Jena.  Zeitschr.,  XT,  1877).  According  to  Kent, 
E.  Ray  Lankester,  and  Mobius,  the  type  species  of  Haliphysema 
(H.  tumanowiczi)  is  a  Protozoan  of  the  Rhizopod  group.  Haeckel 
now  agrees  with  these  authorities  that  the  interior  of  this  last 
named  species  is  filled  with  protoplasm  which  extends  from  the 
single  opening  in  the  form  of  pseudopodia  and  that,  therefore,  this 
form  is  a  Rhizopod,  but  he  also  maintains  that  in  the  species  for- 
merly called  Haliphysema  primordiale  but  now  named  Prophysema 
primordiale  there  is  a  distinct  body  cavity  lined  with  flagellate  epi- 
thelium, so  that  this  species  is  a  true  sponge.  For  further  informa- 
tion see  Rep.  Chall.  Exp.,  Zool.,  XXXII,  part  82,  1889,  p.  26. 


METAZOA  —  PORIFERA.  69 

It  may  be  that  even  pores  do  not  exist,  and  if  so  the 
water  may  be  taken  in  and  thrown  out  at  the  large  open- 
ing, but  in  the  absence  of  any  special  apparatus  for  sift- 
ing the  water  it  is  more  reasonable  to  suppose  that  if  this 
body  is  really  a  sponge,  as  claimed  by  Haeckel,  it  would 
when  living  and  feeding  in  its  native  element  have  tem- 
porary pores  of  minute  size  capable  of  opening  through 
the  walls  between  the  cells.  These  could  furnish  the 
internal  cavity  with  food  of  sufficiently  minute  size  to  be 
handled  by  the  flagella  and  to  be  swallowed  by  the  micro- 
scopic cells  of  the  walls. 

Ascetta  primordialis  Hkl.,  is  the  simplest  form  now 
known  with  certainty  to  be  a  sponge.  If  it  were  deprived 
of  its  skeleton  it  would  represent  the  simplest  sponge 
type,  to  which  Haeckel1  has  given  the  name  of  Olynthus. 

The  fertilized  egg  (PI.  61,  figs.  1-3)  of  this  species  of 
Ascetta  undergoes  segmentation  and  a  one  layered  bias- 
tula  results.  While  still  within  the  body  of  the  parent 
cells  migrate  from  the  surface  of  the  blastula  to  its 
interior  central  cavity  and  this  process  continues  after  the 
larva  has  passed  into  the  water  (PI.  61,  fig.  4)  until  the 
cavity  is  filled  (fig.  5).  The  adult  Ascetta  (PI.  62,  fig.  i  ; 
fig.  2,  the  same  with  a  portion  of  the  external  wall 
removed)  is  a  simple  bag  which  is  capable  of  varying  its 
form  so  that  at  times  it  resembles  a  vase,  a  cylinder,  a 
pear,  or  even  an  egg.  At  one  end  it  is  attached,  and 
at  the  other  there  is  a  large  opening.  The  walls  of  the 
bag  are  thin  and  are  pierced  by  numerous  transient  pores 
which  are  supposed  to  open  anywhere  through  the  walls 
of  the  body,  not  having  any  constant  location.  There 
are  no  persistent  canals  but  the  water  passes  through  the 
shifting  pores  into  the  body  cavity  which  is  lined  with 
flagellate  and  collared  endodermal  cells.  The  middle 
layer  of  cells  known  as  the  mesoderm  is  thin  but  gives 
rise  to  one,  three,  and  four  rayed  spicules  which  are 

!Rep.  Chall.  Exp.,  Zool.,  XXXII,  part  82,  1889. 


70  SYNOPTIC    COLLECTION. 

arranged  in  one  layer.  The  ectoderm  is  colored  blue  in 
the  figure,  and  is  seen  to  invest  the  whole  body  and  cover 
the  projecting  spicules. 

Ascetta  represents  the  group  of  sponges  known  as 
Ascones.  The  "  canal  system  "  of  other  sponges  scarcely 
exists  in  this  group,  since  the  body  cavity  is  a  sac  or  am- 
pulla without  radiating  canals.  If  we  imagine  a  number 
of  Ascetta-like  forms  budding  from  a  common  base  and 
from  each  other's  sides,  so  as  to  form  a  bushy  colony,  we 
have  a  sponge  like  Leucosolenia  (No.  63),  one  of  the 
commonest  on  our  coast.  This  is  a  simple  thin-walled, 
Calcareous  sponge  like  Ascetta  except  that  the  young 
single  tube  gives  rise  to  branches  by  budding,  and  these 
branches  to  others,  until  a  colonial  form  is  produced.  PI. 
63,  figs.  1-3,  show  the  structure  of  the  adult  Leucosolenia 
(species  probably  coriacea  Montague).  A  character  of 
this  genus  is  the  sieve  which  extends  over  the  cloacal 
opening  seen  in  fig.  i,  where  a  portion  of  the  upper  part 
of  the  tube  has  been  cut  away.  Fig.  2  is  a  vertical  sec- 
tion of  one  tube  showing  the  flagellate  cells  of  the  endo- 
derm,  the  large  central  cavity,  the  ectoderm,  and  at  the 
top  the  sieve.  Rising  above  the  sieve,  the  ectoderm  by 
doubling  upon  itself  forms  a  two  layered  ectodermal 
collar.  In  fig.  3  the  sieve  is  separated  from  the  tube. 
Its  cells  have  a  central  portion  containing  a  nucleus 
which  is  more  clearly  seen  in  one  of  the  upper  and  cen- 
tral cells,  where  it  is  indicated  by  a  black  circle.  The 
cells  extend  out  into  a  number  of  processes  and  unite 
with  those  of  other  cells,  thus  forming  a  network  with 
large  openings.  In  this  case  the  body  of  the  cell  forms 
the  node,  but  sometimes  the  node  is  produced  by  the 
union  of  three  cell  processes.  Fig.  4  is  a  spicule  of  this 
genus.  Fig.  5  is  another  species  of  Leucosolenia  (Z. 
dathrus  O.  S.)  which  has  been  described  as  without  large 
openings.  When  seen  in  healthy  living  condition  the 
cloaca  is  widely  extended  (fig.  6)  ;  when  contracted  the 
opening  closes  as  in  fig.  7.  The  sphincter  by  which  the 


METAZOA PORIFERA.  7 1 

work  is  accomplished  is  represented  at  the  base  of  the 
collar  by  a  black  line. 

Several  authors  describe  the  endoderm  in  this  genus  as 
many  layered,  but  Minchin  proved  that  this  appearance 
is  wholly  due  to  contraction.  When  fully  expanded  the 
endoderm  has  only  one  layer,  but  when  contracted  it  is  as 
shown  in  fig.  8 ;  fig.  9  is  a  portion  of  the  endoderm  from 
fig.  8  more  highly  magnified. 

The  genus  Sycandra  is  one  of  the  most  differentiated 
of  the  calcareous  sponges.  Some  of  the  species,  like 
Sycandra  (=Sycon)  raphanus  Hkl.  (No.  65),  are  single, 
while  other  species,  like  Sycandra  arborea  Hkl.,  form  col- 
onies. The  egg  and  spermatozoon  in  Sycandra  raphanus 
Hkl.,  are  transformed  cells  of  the  mesoderm.  The  fertil- 
ized egg  (PI.  64,  fig.  i)  possesses  a  nucleus  and  is  capable 
of  creeping  amoeboid  movements.  In  fig.  2  the  nucleus 
has  divided.  Fig.  3  shows  the  first  cleavage  or  furrowing 
stage  from  above,  and  fig.  3 a  the  same  from  the  side. 
Fig.  4  shows  four  cells,  fig.  5  eight  cells  still  lying  in  pairs  ; 
fig.  5 a  the  same  from  the  side;  fig.  6  sixteen  cells,  fig.  6a 
the  same  from  the  side ;  in  fig.  7  a  large  number  are  rep- 
resented. This  repeated  division  gives  rise  to  a  hollow 
sphere,  the  wall  of  which  is  formed  by  a  single  layer  of 
celis.  PI.  64,  fig.  8,  is  the  blastula  with  its  eight  dark 
granular  cells  surrounding  a  basal  opening,  and  fig.  9  is  a 
further  developed,  entirely  closed  blastula.  In  fig.  10  the 
embryo  has  become  differentiated  into  halves  unlike  each 
other,  for  which  reason  it  is  known  as  an  amphiblastula. 
This  is  probably  a  modification  of  the  primitive  blastula 
already  described,  and  if  so  it  is  a  secondary  and  more 
specialized  form.  The  granular  cells  have  increased  in 
number,  and  are  at  the  broader  end,  while  flagellated  cells 
are  at  the  smaller  end.  In  this  condition  the  embryo 
leaves  the  parent.  Fig.  1 1  is  a  more  advanced  stage  in 
which  the  flagellated  layer  has  become  flattened ;  in  fig. 
12,  it  is  still  more  depressed,  and  in  fig.  13  has  disappeared 
within  (see  note  p.  66).  The  larva  settles  mouth  downward 


72  SYNOPTIC    COLLECTION. 

(fig,  14),  which  is  filled  up  with  granular  cells.  Between 
the  two  layers  of  cells  there  is  a  narrow  bright  zone  which 
Schultze  considers  the  first  indication  of  the  gelatinous 
inter-layer,  mesoderm,  that  reaches  such  a  great  develop- 
ment in  most  sponges. 

The  spicules  appear  in  the  mesoderm,  first  in  the  form 
of  slender,  straight  little  rods  pointed  at  both  ends  (see 
fig.  15),  which  fact  favors  the  view  that  the  first  formed 
spicules  were  one  rayed  and  straight.  They  thicken  as 
they  grow  and  curve  into  a  slightly  S-shaped  form.  After- 
wards three  rayed  and  four  rayed  spicules  are  formed,  one 
of  the  arms  of  which  extends  inward,  while  the  other 
three  are  on  the  surface  and  probably  serve  for  protec- 
tion. 

The  larva  lengthens,  pores  form  in  the  wall,  and  the 
large  opening  at  the  top  breaks  through  the  ectoderm. 
It  is  now  clear  that  this  opening  is"  not  a  mouth  nor  a 
primitive  character,  but  a  secondary  feature,  occurring  in 
a  past  embryonic  stage,  and  is  in  reality  a  cloacal  open- 
ing for  the  ejection  of  the  waste  products  of  the  body. 
The  cells  of  the  endoderm  acquire  collars  and  flagella. 
The  body  cavity  of  the  young  Sycandra  is  now  a  simple 
ampulla  having  as  yet  no  branches.  In  this  stage  it  is 
identical  with  an  adult  Ascon,  like  Ascetta,  which  it 
structurally  represents.  Later  the  mesoderm  thickens, 
the  pores  grow  into,  tubes,  the  ampullaceous  sacs  are 
formed  near  the  food  supply,  the  cells  of  the  body  cavity 
lose  their  flagella,  the  cells  of  the  ampullaceous  sacs 
acquire  collars  and  flagella,  and  from  that  time  the  work 
of  taking  food  and  digesting  it  for  the  use  of  the  other 
cells  is  done  by  them.  Thus  the  single  primitive  diges- 
tive cavity  becomes  a  cloacal  trunk,  pores  become  tubes 
branching  from  this  trunk,  and  the  function  of  the  cavity 
is  transferred  to  the  little  sacs  or  ampullae  formed  in  the 
canals  as  they  are  stretched  out  by  the  thickening  of  the 
mesoderm.  This  is  a  process  of  reduction  resulting  in 
transforming  a  normally  formed,  symmetric,  vase- shaped, 


METAZOA PORIFERA.  7£ 

single  individual  with  one  central  trunk  into  a  creature 
with  overgrown  walls  to  the  body,  with  a  radiating  or 
branching  cavity,  and  with  the  digestive  function  of  the 
central  trunk  transferred  to  expanded  portions  of  the 
branches  or  canals  near  the  exterior.  The  whole  process 
evidently  hinges  on  the  rapid  growth  of  the  mesoderm,. 
because  when  this  is  thin  the  food  supply  is  close  to  the 
central  cavity  ;  when  this  is  thickened  the  pores  must 
become  tubes  ;  when  it  is  still  thicker,  the  tubes  must 
lengthen.  The  food  supply  of  the  body  is  thus  carried 
away  from  the  central  cavity,  and  it  is  but  natural  that 
the  cells  in  the  canals  nearer  the  pores  should  get  more, 
grow  more  and  gradually  make  it  unnecessary  or  impossi- 
ble for  the  cells  farther  inward  to  get  food.  These  last 
must  then  necessarily  suffer  reduction  and  lose  first  the  use 
and  then  the  habit  of  growing  out  collars  and  flagella,  and 
sink  into  the  form  of  epithelial  membrane  cells. 

The  function  of  the  short  canal  leading  into  the 
ampulla  from  the  exterior  is  obviously  to  bring  food  of 
microscopic  size,  and  that  of  the  continuation  of  the  canal 
beyond  the  ampulla  is  to  carry  away  the  excrements  of 
the  ampullaceous  cells.  These  cells  are  voracious  feeders 
and  throw  out  a  large  amount  of  waste  matter  which  is 
carried  into  the  great  central  cavity  by  the  excurrent 
canals,  and  thence  it  is  transported  to  be  ejected  at  the 
cloacal  opening  above. 

We  shall  presently  see  how  in  other  orders  of  sponges 
the  law  of  specialization  by  reduction  has  destroyed  all 
tendency  to  grow  into  symmetrical  shapes,  so  that  the 
Silicea  and  Keratosa  well  deserve  the  designation  of 
amorphous  or  formless,  so  often  bestowed  upon  them. 

This  irregularity  in  form  together  with  greater  com- 
plexity of  structure  is  found  in  Leuconia  aspera  (No.  66) 
which  represents  the  group  of  Leucones,  the  most  spe- 
cialized of  the  calcareous  sponges. 


74  SYNOPTIC    COLLECTION. 

SlLICEA. 

We  cannot  pass  to  the  silicious  sponges  without  con- 
sidering briefly  some  of  the  embryological  facts  relating 
to  their  development.  The  egg  of  most  silicious  sponges 
in  the  earliest  stages  is  solid1  but  becomes  hollow  subse- 
quently. Later  a  granular  mass  accumulates  in  the 
interior  so  that  the  egg  is  again  solid.  The  endoderm  is 
formed  not  by  an  invagination  of  a  portion  of  the  ecto- 
derm, but  by  delamination  from  the  ectoderm,  and  it  is 
this  mass  of  cells  cut  off  from  the  ectoderm  which  fills  up 
the  central  portion  of  the  young  sponge.  Both  Hyatt 
and  Barrois  agree  that  no  gastrula  stage  exists  in  either 
the  silicious  or  the  horny  sponges.  After  the  appear- 
ance of  the  ampullaceous  sacs  and  the  spicules,  the  larva 
becomes  fixed  by  the  collar  at  the  oral  end  of  its  body. 
The  canals  and  pores  form  and  afterward,  probably 
through  the  mechanical  pressure  of  the  water,  the  cloacal 
opening  breaks  through  the  ectoderm.  It  will  be  seen 
that  here,  as  in  the  calcareous  sponges,  this  opening  is 
not  comparable  with  the  mouth  of  other  animals,  but  is  a 
secondary  formation  and  in  function  a  cloaca. 

Halisarca  (=  Oscarclla)  lobularis  O.  Schmidt  (If.  dujar- 
dini  Duj.,  PI.  67,  encrusting  a  stone),  may  be  one  of  the 
simplest  of  the  silicious  sponges.  Its  cells  are  less  differ- 
entiated than  those  of  most  sponges.  The  ectodermal  cells 
retain  their  fiagella  throughout  life,  and  the  cells  of  the  mes- 
oderm  are  not  modified,  as  in  the  more  specialized  forms.2 
There  is  no  skeleton,  and  in  the  absence  of  positive 
information  it  is  possible  that  Halisarca  is  one  of  the 
primitive  forms.  Authorities  differ  with  regard  to  the 
origin  of  this  genus,  and  it  is  at  present  impracticable  to 
determine  whether  it  is  a  reduced  form,  a  descendant  of 

1  Hyatt,  Proc.  Boston  Soc.  Nat.  Hist.,  XIX,  1878,  p.  12. 

2  Sollas,  Quart.  Journ.  Micr.  Sci.,  XXIV,  1884,  £.  618. 


METAZOA PORIFERA.  75 

genera  with  skeletal  structures  which  has  reached  its 
present  condition  by  reduction,  or  whether  it  is  an  existing 
representative  of  a  primitive  type  which  has  never  had  any 
skeletal  structures.  Whatever  way  the  result  has  been 
arrived  at,  the  existing  Halisarca  is  obviously  a  skeleton- 
less  kind  of  silicious  sponge,  and  can  be  used  to  show  what 
such  forms  are  like.  It  is'  a  fleshy  animal  with  the  typical 
characters  of  pores,  canals,  ampullaceous  sacs,  and  cloa- 
cal  opening.  The  genus  is  interesting  because  it  increases 
not  only  by  eggs  but  also  by  a  process  known  as  budding 
which  is  essentially  the  same  as  that  of  division  so  com- 
mon among  the  Protozoa.  In  this  case,  however,  there 
is  not  an  equal  division  of  the  body,  but  a  part  separates 
from  the  rest  and  becomes  a  new  animal. 


SILICEA.  —  HEXACTINELLIDA. 

This  group  is  represented  by  fossils,  and  living  mem- 
bers are  mostly  found  in  the  deep  seas.  Although  the 
oldest  silicious  sponges  probably  possessed  separate  spic- 
ules,  yet  on  the  death  of  the  animal  these  would  fall  apart 
and  be  swept  away  and  deposited  along  with  other  re- 
mains, so  that  no  satisfactory  inferences  can  be  drawn  in 
regard  to  the  sponges  possessing  them. 

The  predominating  six  rayed  spicules  of  the  group 
have  been  shown  to  be  simply  a  modification  of  the  three 
rayed  form  which  we  have  found  among  the  Calcarea. 
It  has  also  been  proved  that  the  anatomical  structure  and 
the  development  of  these  sponges  are  in  some  ways  like 
those  of  the  calcareous  sponges.  For  these  reasons,  and 
because  the  group  is  found  in  the  oldest  geological  forma- 
tions, the  Hexactinellida  are  considered  as  the  more  gen- 
eralized of  the  silicious  sponges. 

Ventriculites  (No.  68),  often  occurring  in  the  chalk,  is 
made  up  of  six  rayed  spicules  which  are  always  fused 
together.  It  is  more  or  less  cup-shaped  with  a  wide  cen- 


76  SYNOPTIC    COLLECTION. 

tral  hollow.  In  Hyalonema  sieboldi  Gray  (No.  69),  the 
cup-shaped  body  is  supported  on  a  long  tuft  of  silicious 
spicules,  by  means  of  which  the  animal  is  anchored  in 
the  mud.  These  rooting  spicules  are  sometimes  two  feet 
long,  while  the  spicules  of  the  body  are  varied  and  beau- 
tiful in  design. 

The  probable  ancestor  of  Euplectella  speciosa  Q.  &  M., 
was  one  of  the  Dictyospongidae  which  were  vase-shaped 
sponges  composed  of  spicules  that  united  to  form  a  frame- 
work similar  to  that  of  Euplectella.  This  has  disap- 
peared from  the  fossils  but  the  tracery  of  the  fibers  may 
be  seen  on  their  surfaces.  In  the  living  Euplectella  (No. 
70)  the  delicate  skeleton  is  covered  by  a  grayish  brown 
fleshy  matter  and  skin.  It  is  interesting  to  note  that  the 
young  Euplectella  has  the  spicules  separated,  but  with  the 
growth  of  the  animal  fusion  takes  place  to  form  the  deli- 
cate framework.  The  sponge  skeleton  consists  of  longi- 
tudinal and  circular  silicious  strands  intersecting  in  such 
a  way  as  to  form  meshes.  Besides  these  there  are  ridges 
of  fibers  which  run  spirally  around  the  skeleton.  The 
upper  end  is  closed  by  a  sieve-like  plate,  while  at  the 
lower  end  long  silicious  spicules  extend  downward  to 
anchor  the  animal  in  the  mud.  In  dried  specimens  of 
the  skeleton  these  long,  fiber-like  spicules  are  usually  bent 
upward  around  the  base  of  the  sponge,  and  they  are  also 
thus  represented  in  drawings.  Such  specimens  and  fig- 
ures are  misleading,  since  these  spicules  always  extend 
downward  and  outward  for  the  purpose  of  firmly  anchor- 
ing the  animal. 

An  interesting  case  of  commensalism  is  offered  by 
Euplectella,  since  it  often  harbors  within  the  hollow  of  its 
vase-like  structure  a  little  shrimp,  Spongicola. 

In  the  Hexactinellida  there  is  no  drainage  canal  sys- 
tem, as  the  large  ampullaceous  sacs  open  directly  into  the 
great  cloacal  tube  which  is  closed  at  the  opening  above 
by  the  sieve-like  plate. 

The%  members  of  this  group  resemble  the  Calcarea  in 


METAZOA PORIFERA.  77 

being  more  symmetrical  and  constant  in  form  than  the 
members  of  othef  orders  of  Silicea.  They  also  stand 
correspondingly  near  to  the  Calcarea  in  their  organiza- 
tion, as  has  already  been  stated.  The  mesoderm  is  not 
so  thin,  but  it  approximates  to  the  condition  of  that  of  the 
more  primitive  calcareous  sponges,  and  in  accord  with 
this  the  excurrent  canals  are  not  found,  and  the  ampullae 
open  directly  into  the  cloacal  trunk  in  some  forms.  Thus 
the  organization  is  just  a  grade  more  specialized  than  in 
the  Ascones  with  their  digestive  cells  in  the  central  trunk, 
and  less  specialized  than  Sycones  with  their  ampullae  in 
the  canals  of  the  lateral  branches  of  the  water  system. 


SILICEA.  —  LITHISTIDAE. 

These  forms  have  a  thick  stony  wall  and  irregular 
spicules  some  of  which  are  cleft  into  ragged  branches. 
The  fossil  Tragos  (No.  71)  is  a  representative.  It  is 
shaped  like  a  funnel  and  the  exterior  wall  is  often  wrinkled 
concentrically. 


SILICEA. — TETRACTINELLIDA. 

Tetilla  sandalina  Sollas  (PL  72,  fig.  i)  is  a  representa- 
tive of  the  simple  Tetractinellida.  It  has  a  single  open- 
ing at  one  end  with  papillae  at  the  other.  The  outer 
portion  of  the  sponge  is  soft,  not  differing  essentially 
from  the  inner.  The  mesoderm  is  slightly  developed. 
The  ampullaceous  sacs  (fig.  2)  with  their  flagellate  cells 
are  large,  and  open  by  a  wide  mouth  into  the  excurrent 
canals.  The  spicules  vary  from  a  straight  rod  to  an 
S-shaped  form  (fig.  3).  They  are  seen  in  fig.  2,  where 
the  straight  ones  overlap,  forming  "spicular  fibers." 

Tethya  (No.  73;  PL  74,  figs,  i,  2)  has  a  spherical 
form  with  one  or  more  small  openings.  The  outer  sur- 


fO  SYNOPTIC    COLLECTION. 

face  of  the  ectoderm  is  differentiated  into  a  hardened 
wall  or  cortex  with  a  distinct  fibrous  layer.  The  skeleton 
in  Tethya  has  a  radiate  arrangement.  The  spicules 
when  typical  have  a  long  straight  axis  with  three  curved 
horns.  Besides  these  there  are  straight  spicules  with 
both  ends  alike,  and  also  star-like  silicious  forms.  Fig.  2 
is  a  vertical  section  of  Tethya  showing  its  system  of 
tubes,  the  cloacal  opening  to  one  side,  and  the  silicious 
threads  extending  from  the  base.  The  power  of  adapta- 
tion possessed  by  most  animals  in  a  greater  or  less  degree 
is  strikingly  seen  in  Tethya.  With  a  rounded  form  and 
a  yellowish  color  which  have  given  it  the  name  of  "the 
orange  of  the  sea"  (see  fig.  i),  it  has  succeeded  in  secur- 
ing a  firmer  hold  by  means  of  long,  tough,  silicious 
threads  (PI.  74)  which  act  as  anchors  penetrating  the 
mud  and  holding  the  growing  sponge  upright.  The  spe- 
cies shown  has  a  peculiar  adaptation  of  this  habit,  having 
a  network  of  silicious  threads  like  a  mat  of  coarse  wool 
on  its  base.  These  catch  the  fine  gravel  sifted  out  of  the 
mud  by  the  movements  of  the  animal  caused  by  the 
waves,  and  this  gravel  makes  its  lower  side  much  the 
heavier.  If  now  the  animal  is  upset  or  swept  away  by 
the  current  or  waves,  the  gravel  acting  as  ballast  will 
always  serve  to  keep  it  right  side  up. 

One  of  the  most  complex  forms  of  this  group  is  Geodia 
(No.  75).  Here  the  outer  part  is  differentiated  to  form 
a  cortex  and  the  mesoderm  is  thick.  The  spicules  are 
unusually  large  and  can  be  seen  with  the  naked  eye. 

SlLICEA. MONAXONIA. 

There  is  no  sharp  line  of  division  between  the  Tetrac- 
tinellida  and  the  Monaxonia.  Suberites  (No.  76  ;  No.  77, 
dried  specimen)  is  instructive,  since  it  has  adapted  itself 
to  a  free  life  on  shifting  sands.  Its  pores  are  so  small 
and  the  structure  so  dense  that  the  sand  cannot  pass 


METAZOA PORIFERA.  79 

Hito  the  sponge,  and  its  lightness  keeps  it  from  being 
buried  (Hyatt,  Stand.  Nat.  Hist,  I,  1885,  p.  66).  The 
Suberitidae  offer  fine  examples  of  spiral  and  radiate 
structure  of  the  skeleton.  This  is  seen  in  Stylocordyla 
stipitata  var.  globosa  (PI.  78,  figs.  1-3).  Fig.  i  shows 
spiral  arrangement  of  the  bands  of  spicules  in  one  speci- 
men ;  fig.  2  is  a  longitudinal  section  of  another  speci- 
men, showing  radiate  structure;  and  fig.  3  is  a  cross 
section  of  the  same,  showing  the  longitudinal  spicules  of 
the  stem  by  which  the  sponge  is  attached  and  the  radiate 
arrangement  of  the  spicules  of  the  body  part.  The  ends 
of  the  spicules  of  the  stem  which  have  been  cut  are  seen 
near  the  center  of  the  drawing.  In  most  of  the  Monaxo- 
nia  there  is  more  or  less  horny  cementing  material  called 
spongin.  It  is  interesting  to  note  that  the  chemical 
composition  of  this  substance  is  similar  to  that  of 
chitin,  Krukenberg  having  given  it  the  chemical  for- 
mula C30H46N9O13,  while  that  of  chitin  is  C15H26N2O10. 

Another  member  of  the  Suberitidae  is  Raphiophora 
patera  Gray  (No.  79),  which  is  on  the  top  of  Section  i. 
This  is  one  of  the  largest  species  of  the  Porifera  and  its 
size  and  shape  have  given  it  the  name  of  Neptune's  Cup. 

Cliona  (No.  80)  is  a  borer  into  the  living  and  dead 
shells  of  mollusks,  especially  the  oyster,  and  into  lime- 
stone, etc.  PI.  81,  fig.  i,  represents  the  openings  of  the 
young  Cliona  enlarged,  and  fig.  2  shows  the  work  of  the 
sponge  in  the  interior  of  the  shell.  Just  beneath  the 
outer  surface  is  a  series  of  excavations,  and  narrow 
passages  connect  these  with  another  series  of  cavities 
below.  When  the  shell  is  completely  mined,  the  sponge 
swells  out  in  a  bulbous  mass  on  the  outside  (fig.  3). 
Having  destroyed  the  shell,  it  will  takesr>nd  into  its  body, 
as  seen  in  fig.  4,  which  is  a  section  of  the  sponge  show- 
ing fine  black  sand  in  the  tubes  and  cavities  of  the  inte- 
rior. It  also  surrounds  stones  and  takes  them  in,  as  seen 
in  fig.  5. 

No.   82    is    a   specimen    of  Italian    marble    bored    by 


80  SYM  OPTIC   COLLECTION. 

Cliona.  This  marble  lay  in  water  seven  years,  during 
which  time  the  borings  from  one  and  a  half  to  two  inches 
in  depth  were  made. 

Dr.  Leidy1  states  that  the  large  and  numerous  shells  of 
the  dead  oysters  in  an  extensive  bed  planted  by  Beasley 
at  Great  Egg  Harbor,  were  so  completely  riddled  in  two 
years  by  the  Cliona  that  they  were  crushed  with  ease. 

The  process  of  boring  is  both  mechanical  and  chemi- 
cal, and  the  habit  seems  to  be  an  acquired  one  which  has 
been  transmitted,  Nassonow2  stating  that  the  young  begin 
to  bore  before  the  formation  of  the  spicular  skeleton. 
The  body  puts  forth  fleshy  outrunners  and  it  is  largely 
these  that  do  the  work.  .  It  is  also  probable  that  an  acid 
is  secreted  which  aids  in  the  work.  Unlike  most  sponges 
the  Cliona  discharges  its  eggs  into  the  water  before  the 
formation  of  the  embryo  has  begun,  so  that  the  whole 
development  goes  on  outside  the  parent. 

The  skeleton  is  made  up  of  one  rayed  spicules,  many 
of  which  are  pin-shaped.  Ryder^  has  shown  that  the 
protoplasm  in  sponges  executes  delicate  fluctuating  move- 
ments, so  that  in  Cliona  as  in  Stylocordyla  and  many 
other  genera,  the  needles  are  drawn  into  bundles  or  rows 
extending  in  particular  directions. 

In  the  fresh-water  sponges  (Spongilla,  No.  83)  the 
silicious  spicules  are  numerous,  while  a  small  quantity  of 
spongin  is  developed.  These  sponges,  although  probably 
derived  from  some  marine  form,  yet  develop  a  structure 
which  is  never  found  in  the  latter  ;  namely,  the  statoblasts 
or  winter  buds.  These  are  internal  buds  which  are 
enclosed  in  horny  cases  with  peculiar  spicules.  When 
the  sponge  dies  the  winter  buds  survive  ;  these  are  so 
slightly  affected  by  heat  or  cold  that  by  them  the  perpet- 
uation of  the  species  is  rendered  more  sure.  In  addition 

iProc.  Acad.  Nat.  Sci.  Phila.,  VIII,  1857,  p.  162. 
2Zeitschr.  f.  wiss.  Zool.,  XXXIX,  1883,  p.  300. 
3Amer.  Nat.,  XIII,  May,  1879. 


METAZOA PORIFERA.  81 

to  the  peculiar  spicules  just  named  there  are  two  other 
kinds  of  spicules  forming  the  skeleton  and  strengthening 
the  dermis.  An  interesting  specimen  allied  to  Spongilla 
lacustris  has  been  described  by  Edward  Potts.  This 
sponge  is  found  incrusting  marine  organisms  such  as  bar- 
nacles and  the  calcareous  tubes  of  Serpula,  in  the  fresh 
water  of  a  creek  in  the  southwestern  part  of  Florida. 
The  presence  of  the  barnacles  can  only  be  accounted  for 
by  the  action  of  the  strong  southeast  winds  which  back 
up  the  salt  water  into  the  rivers  and  creeks.  The  young 
barnacles,  having  followed  the  influx  of  salt  water  and 
attached  themselves  to  the  rocks  on  the  bottom,  may  have 
attained  a  portion  of  their  growth  while  immersed  in  fresh 
water  after  the  subsidence  of  the  salt  water.  If  this  be 
true  it  is  suggestive  of  the  possibility  of  the  conversion  of 
the  marine  barnacle  into  a  fresh-water  species.  The 
sponges  already  spoken  of  as  occurring  on  these  animals 
have  the  peculiar  habit  of  hiding  away  the  winter  buds 
within  the  barnacles  or  in  the  tubes  of  the  Serpula. 

A  sponge  (Reniera),  closely  related  to  the  Chalinula 
next  to  be  described,  is  said  to  possess  thread  cells  or 
nematocysts  which  were  formerly  supposed  to  be  the 
exclusive  possession  of  the  next  branch,  the  Coelentera, 
but  which  have  already  been  found  in  the  Protozoa.  In 
this  group  the  embryo  has  a  pigmented  spot  on  one  end 
of  its  oval  body  which  may  perhaps  be  considered  as  an 
eye.1 

Chalinula  oculata  Pallas  is  of  especial  interest  to  New 
Englanders  since  it  grows  abundantly  along  the  eastern 
coast.  In  this  sponge  the  spicules  are  straight  and  exist 
as  vestiges,  while  the  horny  matter  has  increased  in 
quantity. 

Keller2  has  observed  and  figured  the  consecutive  stages 


1  Lendenf eld,  Mon.  Australian    Sponges,   Proc.  Linn.    Soc.  New 
South  Wales,  IX,  part  2,  1884,  p.  324. 
2Zeitschr.  f.  wiss.  Zool.,  XXXIII,  1880,  p.  317. 


82  SYNOPTIC    COLLECTION. 

of  development  of  another  species,  Chalinula  fertilis 
Keller,  and  by  so  doing  has  thrown  strong  light  on  many 
important  points.  Besides  the  asexual  mode  of  increase 
through  budding,  there  occurs  a  sexual  propagation,  the 
latter  probably  taking  place  only  in  the  spring.  In  this 
sponge  the  sexes  are  distinct,  the  females  being  two  or 
three  times  larger  than  the  males.  As  soon  as  the  forma- 
tion of  the  egg  begins  the  ordinary  brown  color  of  the 
female  changes  to  red,  becoming  in  very  vigorous  animals 
almost  a  cherry  red.  This  color  disappears  after  fertili- 
zation or  at  the  beginning  of  the  egg  furrowing,  and  the 
female  becomes  ochre  yellow  at  the  time  the  larvae 
swarm  out.  The  males  do  not  change  their  color.  PL 
84,  fig.  i,  is  a  young,  unfertilized  egg  which  possesses 
amoeboid  movements.  Fig.  2  represents  a  spermatozoon 
which  reminds  one  of  a  flagellate  Protozoan.  Fig.  3  is  a 
mature  egg  which  has  become  spherical  in  form  and  sur- 
rounded by  a  capsule.  Nutritive  mesoderm  cells  are  seen 
near  it.  The  capsule  is  formed  early  and  it  must  be 
assumed,  therefore,  that  the  spermatozoon  pierces  it  in 
order  to  reach  the  egg  within.  After  impregnation,  the 
furrowing  takes  place  quickly,  and  normally  covers  from 
twenty  to  thirty  hours.  It  is  total,  but  the  cells  are  un- 
equal in  size  and  there  is  no  segmentation  cavity.  Fig. 
4  shows  the  first  two  furrowing  cells  ;  fig.  5,  the  stage 
with  four  cells  lying  in  a  plane.  In  fig.  6  (figs.  6-9  drawn 
without  capsule)  these  cells  have  arranged  themselves  in 
a  pyramidal  form,  the  large  cell  being  the  parent  cell  of 
the  endoderm.  Fig.  7  has  seven  cells  and  fig.  8  fourteen  . 
cells.  Here  the  two  large  endoderm  cells  are  partly 
surrounded  by  ectoderm  cells.  In  fig.  9  the  endoderm 
forms  a  central  mass  of  cells  and  appears  at  the  peri- 
phery as  a  plug.  The  other  cells  on  the  surface  are  ecto- 
dermic.1 

1According  to  Wilson  (see  "  Notes  on  the  Development  of  some 
Sponges,"  Journ.  of  Morphology,  V.,  no.  3,  1891,  p.  516),  it  is 
probably  not  the  endoderm  that  protrudes  at  this  pole,  but  the 
ectoderm,  which  is  greatly  flattened  over  this  region. 


METAZOA PORIFERA.  83 

PI.  84,  fig.  10,  is  a  later  stage  still  enclosed  in  the  cap- 
sule ;  the  cylindrical  ectoderm  cells  have  already  devel- 
oped whips ;  the  plug  is  strongly  pigmented.  In  the 
mesoderm,  flint  needles  (colored  blue  in  the  figure)  have 
begun  to  form.  They  are  at  first  irregular  and  scattered. 
It  is  a  fact  of  great  significance  that  the  spicules  appear 
before  the  formation  of  the  cementing  material,  spongin. 
The  latter  is  probably  a  secretion  of  the  mesoderm,  and 
is  deposited  according  to  need  in  layers  around  the 
spicules  (see  PI.  84,  fig.  20).  This  furnishes  a  strong 
argument  in  favor  of  the  view  that  a  part  at  least  of  the 
horny  sponges  are  descendants  of  the  silicious  sponges. 
PI.  84,  fig.  ii  is  the  free-swimming  larva  which  has 
escaped  from  the  capsule  and  the  body  of  the  parent. 
As  it  swims  the  pointed  end  is  directed  forward.  No 
inner  cavity  yet  exists.  Figs.  12  and  13  represent  the 
larva  just  before  becoming  attached.  It  is  now  much 
flattened  (fig.  12,  peripheral  view;  fig.  13,  broadside). 
About  thirty-six  hours  after  settlement,  it  looks  as  shown 
in  fig.  14.  The  isolated  spicule  in  the  larva  is  seen  in 
fig.  15,  still  lying  within  its  cell.  No  cavity  had  appeared 
two  and  a  half  days  after  settlement.  Fig.  16  is  a  view 
of  the  young  sponge  (natural  size)  five  days  after  becom- 
ing attached.  The  ampullaceous  sacs  with  whipped  cells 
are  now  numerous  and  open  into  a  wide  cavity.  The 
cloacal  opening  arises  on  this  day  (the  fifth)  by  the  body 
cavity  breaking  through  the  outside  wall,  and  on  the 
same  day  and  by  a  similar  process  the  pores  are  formed 
(see  fig.  17,  a  vertical  section  of  the  sponge  at  this  stage). 
When  the  canals  and  pores  appear  the  stream  of  water 
acts  effectively  upon  the  position  of  the  needles  and 
fortns  radial  lines.  Figs.  18  and  19  give  us  the  external 
and  internal  structure  of  the  adult.  Fig.  20  shows  the 
spicules  of  the  adult  bound  together  by  spongin.  Fig.  2 1 
represents  a  small  female  colony.  No.  85  is  a  larger 
adult. 

The  following  is  a  summary  of  the  time  required  for 
the  six  stages  of  development,  as  given  by  Keller. 


84  SYNOPTIC    COLLECTION. 

First :  Duration  of  the  furrowing  period,  thirty  hours. 
Second:  Swarming  out  of  the  larvae,  continuing  to  the 
end  of  the  second  day.  Third  :  Free-living  larva  stage 
during  third,  fourth,  and  fifth  days.  Fourth  :  Settlement 
on  fifth  day.  Fifth  :  Formation  of  the  ampullaceous  sacs 
and  of  the  body  cavity  on  the  eighth  day.  Sixth  :  Break- 
ing through  of  the  cloacal  opening  and  the  formation  of 
the  skin  pores. 

According  to  Dendy  l  the  West  Indian  Chalininae 
offer  the  strongest  arguments  in  favor  of  the  view  that 
the  Keratosa  have  descended  polyphyletically  from  sev- 
eral distinct  groups  of  silicious  sponges.  In  different 
species  of  the  same  genus  he  has  traced  the  gradual 
reduction  and  disappearance  of  the  spicules  until  forms 
are  reached  like  Spinosella  maxima  Dendy,  and  Spinosella 
plicifera  D.  &  M.,  which  sometimes  still  contain  traces  of 
the  spicules  imbedded  in  the  horny  fiber,  and  apparently 
on  the  verge  of  disappearance,  while  at  other  times  they 
contain  no  spicules  whatever,  and  yet  the  specimens  with 
spicules  and  those  without  are  specifically  indistinguish- 
able. No.  86  Tuba  (=  Spinosella'2)  vaginalis  Lam.  var. 
sororia,  and  No.  87,  Tuba  scrobiculata  D.  &  M.,  show  the 
variation  in  form  peculiar  to  this  genus  of  sponges. 


KERATOSA. 

The  Keratosa  are  not  found  in  a  fossil  condition. 
They  are  probably  the  specialized  descendants  of  silicious 
forms,  some  of  which  have  already  been  described. 
This  view  finds  additional  confirmation  in  the  researches 
of  Maas  8  who  states  that  the  embryological  development 

1  Trans.  Zool.  Soc.  London,  XII,  part  14,  1890. 

2  Vosmaer  in  1885  substituted  the  generic  name  of  Spinosella  for 
the  familiar  one  of  Tuba. 

3  Zool.  Jahrb.,  Anat.,  VII,  Heft  2,  1893,  p.  331. 


METAZOA PORIFERA.  85 

of  the  horny  sponges  is  so  similar  to  that  of  the  silicious 
sponges  that  a  precise  description  would  be  mere  repeti- 
tion. According  to  this  author  the  horny  sponges  are 
more  nearly  related  to  the  silicious  than  are  the  silicious 
sponges  among  themselves  ;  so  that  a  separation  of  an 
independent  order  of  fibrous  sponges  does  not  seem  justi- 
fied from  a  morphological  point  of  view  but  only  as  a 
matter  of  convenience. 

One  of  the  simplest  sponges  belonging  to  this  group  is 
Ammolynthus  prototypus  Hkl.  (PI.  88,  fig.  i).  A  cross 
section  (partly  diagrammatic)  is  seen  in  fig.  2  which 
exhibits  the  egg  with  its  nucleus  and  nucleolus.  The 
sponge  that  grows  from  this  egg  consists  of  a  simple  tube 
with  one  large  opening  (fig.  i).  The  body  cavity  is  sim- 
ple (fig.  2)  and  without  branches,  the  canal  system  being 
similar  to  that  of  the  Ascones  among  the  Calcarea.  The 
walls  of  the  tubular  body  are  pierced  by  many  pores 
through  which  the  water  enters  ;  this  flows  into  the  large 
central  cavity  which  is  lined  with  endodermal  flagellate 
cells.  No  skeleton  is  developed,  but  the  animal  takes  up 
Radiolarian  shells  (see  figs,  i,  2)  and  in  this  way  makes 
a  false  skeleton. 

This  sponge  and  the  other  species  of  the  group  to 
which  it  belongs  are  remarkable  examples  of  symbiosis 
already  seen  among  the  Protozoa  (see  p.  44) .  In  place 
of  the  horny  fibers  of  other  keratose  sponges  it  has  the 
tubes  of  a  hydroid  which  serve  the  purpose  of  a  support- 
ing framework. 

Ammosolenia  (PL  88,  fig.  3)  is  similar  in  structure  to 
Ammolynthus  but  is  a  colonial  sponge  corresponding  to 
the  Leucosolenia  in  the  calcareous  group. 

An  extremely  interesting  form  is  represented  by  PI.  89, 
fig.  i.  Here  in  Darwinella  australiensis  Carter,  we 
have  a  sponge  with  spicules  made  of  spongin  instead  of 
carbonate  of  lime  or  silica.  No  spicules  are  wholly  min- 
eral, however,  and  this  being  the  case,  it  is  not  difficult  to 
understand,  as  pointed  out  by  R.  von  Lendenfeld,  how 


86  SYNOPTIC    COLLECTION. 

the  inorganic  silica  may  have  been  replaced  by  the 
organic  horny  material.  The  spicules  vary  but  are  built 
on  the  triaxon  plan.  Besides  the  horny  spicules  there  are 
horny  fibers  which  do  not  unite  to  form  a  network. 

We  have  here  just  those  conditions  which  one  might 
expect  to  find  in  a  transitional  form  between  the  silicious 
and  the  horny  sponges  where  the  silica  is  replaced  by 
spongin,  and  where  the  horny  skeleton  has  not  yet  become 
the  complex  network  seen  in  the  more  specialized  genera. 

The  canal  system  of  Darwinella  is  simple  and  im- 
branched  and  the  ampullaceous  sacs  are  of  large  size. 

Another  genus,  Aplysilla,  is  placed  near  Darwinella 
which  it  resembles  by  having  large  ampullae,  simple 
canals,  and  isolated  erect  horny  fibers,  but  it  differs  from 
this  genus  by  having  no  horny  spicules.  These  have 
wholly  disappeared  and  the  skeleton,  now  entirely  fibrous, 
is  destined  to  develop  in  succeeding  more  specialized 
forms  until  a  labyrinthian  network  of  fibers  is  the  result. 

Hircinia  campana  Hyatt  (No.  90),  is  normally  vase- 
shaped,  but  is  subject  to  great  variation,  sometimes 
becoming  tubular,  as  proved  by  specimen  No.  91.  It  has 
been  shown l  that  although  this  variation  is  great  as 
compared  with  the  more  specialized  invertebrates,  never- 
theless a  formula  may  be  given  which  expresses  the 
possible  range  of  variation  in  every  species.  One  of  the 
simplest  of  the  Hircinia  (If.  cactus)  has  a  skeleton  com- 
posed of  simple  main  fibers  which  contain  foreign  sub- 
stance and  slightly  branched  connecting  fibers  which  are 
free  from  foreign  particles.  The  spongin  of  which  the 
fibers  are  composed  is  stratified  and  a  granular  axial 
thread  is  present. 

In  Verotigia  fistnlaris  Bon.  (Nos.  92,  93),  the  fibers 
are  so  large  that  their  tubular  form  can  be  seen  with  the 
eye.  They  are  loosely  put  together,  but  the  main  and 

1  Hyatt,  Mem.  Boston  Soc.  Nat.  Hist.,  II,  pt  IV,  no.  5,  1877,  p. 
483- 


METAZOA  —  PORIFERA.  87 

connecting  fibers  are  not  easily  determined.  The  two 
specimens  show  variation  in  form. 

Carteriospongia  radiata  Hyatt,  var.  dulcina  (No.  94), 
is  one  of  the  most  beautiful  of  horny  sponges.  It  grows 
upward  from  a  stem  in  the  form  of  delicate  fronds.  The 
surface  of  the  fronds  is  smooth  and  the  fibers  are  so 
closely  woven  that  they  form  a  veil  on  the  upper  side, 
and  sometimes  on  the  lower,  which  bridges  over  the 
inequalities  of  the  interior.  Large  specimens  of  Carterio- 
spongia may  have  as  many  as  sixty  branches. 

The  most  complex  representatives  of  fhe  group  of 
horny  sponges  belong  to  the  family  Spongidae.  Nos.  95— 
97  are  Spongia  tubulifera  Lam.,  var.  rotunda  Hyatt.  No. 
95  is  a  vertical  section  through  the  body  of  the  sponge, 
showing  the  flesh,  the  large  central  tubes  with  radiating 
tubes,  and  the  openings  of  other  tubes  which  run  in  all 
directions  through  the  sponge  body.  No.  96  is  a  dried 
specimen  of  the  flesh  and  skeleton,  and  No.  97  is  the 
skeleton  with  the  flesh  removed.  The  fibers  are  fine  and 
soft.  No.  98  is  another  species  of  the  same  genus,  S. 
molissima  Schm.,  in  which  the  fibers  are  dense  and  closely 
woven. 

This  collection  of  sponges  with  •  the  supplementary 
drawings  illustrates  the  following  points. 

The  sponge  animal  arises  from  an  egg  which  resem- 
bles many  adult  Protozoa. 

The  egg  in  its  further  development  passes  through  a 
blastula  stage,  thereby  representing  the  adult  Volvox  of 
the  Mesozoa. 

The  blastula  stage  is  succeeded  in  most  sponges  by 
a  solid  parenchymella  stage.  The  endoderm  arises  by  a 
process  either  of  immigration  or  of  delamination  of  cells, 
and  a  two  layered  organism  is  produced.  Subsequently 
an  internal  cavity  and  an  external  mouth  opening  are 
formed.  This  stage  is  transient,  since  by  the  formation  of  a 
middle  layer  or  mesoderm  the  adult  always  becomes  a 
three  layered  organism. 


88  SYNOPTIC    COLLECTION. 

The  flagellate  and  collared  cells  of  the  endoderm  are 
unique,  and  may  indicate  genetic  relationship  with  the 
Flagellata  of  the  Protozoa  or  parallelism  of  development 
in  two  different  groups. 

When  fixation  takes  place,  the  sponge  settles  with  its 
mouth  downward,  after  which  the  cloaca  breaks  through 
the  ectoderm,  proving  thereby  that  this  opening  is  not  a 
primitive  but  a  secondary  character. 

The  primitive,  adult,  ancestral  form  of  the  group  of 
sponges  was  a  simple,  skeletonless,  tubular  organism  with 
a  water  system  consisting  of  transient  pores,  and  a  central 
cavity  with  no  canals  and  no  ampullaceous  sacs. 

This  primitive  form  is  inherited  with  certain  modifica- 
tions by  many  of  the  simpler  members  of  the  different 
orders  of  sponges.  By  a  differentiation  of  this  primitive 
form  the  most  specialized  sponges  with  canals  and  sacs 
have  arisen. 

The  calcareous  and  silicious  sponges  are  considered 
the  most  generalized  and  the  keratose  sponges  the  most 
specialized  for  the  following  reasons. 

The  calcareous  sponges,  as  a  group,  are  most  rudimen- 
tary in  structure.  The  Silicea  are  found  in  ancient  geo- 
logical formations  and  in  the  deep  seas  of  to-day,  while 
the  Keratosa  do  not  occur  as  fossils. 
-  The  history  of  the  development  of  the  transitional 
forms,  the  silica-and-keratose  sponges,  proves  that  the 
silica  appears  first  and  afterward  the  spongin  is  devel- 
oped. 


METAZOA COELENTERA.  89 

\ 

COELENTERA. 

Section  2.  —  HYDROZOA. 

HYDROPHORA. 

If  we  consider  the  Protozoa  arid  Mesozoa  as  constituting 
the  trunk  of  our  genealogical  tree  and  the  Porifera  as  the 
first  short  branch  sent  off  from  this  trunk,  then  the  Coelen- 
tera  through  comparative  simplicity  of  structure  represent 
the  second  branch.  Although  an  unbroken  line  of  descent 
from  the  many-celled,  one  layered  Mesozoan  to  the  Hydro- 
zoa  (the  most  generalized  class  of  the  Coelentera)  cannot 
be  traced,  yet  it  is  not  difficult  to  conceive  of  an  animal 
like  a  primitive  Hydroid  arising  from  an  ancestral  form 
similar  to  that  which  produced  in  course  of  generations 
the  simplest,  tubular  sponges. 

The  two  theories  held  by  naturalists  in  regard  to  the 
origin  of  the  Metazoa  have  already  been  stated  (see  p. 
64).  Briefly  summarized  it  may  be  said  that,  according 
to  one  view,  the  one  layered  blastula  gives  rise  to  a  two 
layered  invaginate  gastrula,  the  ancestral  form  of  which, 
the  Gastraea,  has  not  been  discovered.  The  gastrula  in 
turn  produces  a  form  that  is  two  layered  in  youth  and 
three  layered  in  the  adult,  like  the  sponge. 

According  to  the  second  theory,  the  blastula  gives  rise 
to  a  solid  parenchymella  which  in  time  becomes  two  lay- 
ered and  hollow  and  afterward  is  provided  with  an  open- 
ing. In  this  case  no  primitive  invaginate  gastrula  exists. 
The  Hydrophora  or  Hydromedusae,  now  to  be  described, 
illustrate  almost  universally  the  second  mode  of  develop- 
ment, and  some  naturalists l  even  maintain  that  not  a  single 
invaginate  hydroid  gastrula  has  been  observed. 

1  W.  K.  Brooks,  Mem.  Boston  Soc.  Nat.  Hist.,  Ill,  no.  12,  1886, 
p.  401. 


90  SYNOPTIC    COLLECTION. 

It  is  probable  that  the  ancestor  of  the  class  of  Hydroids, 
like  that  of  the  Porifera,  was  a  fleshy  animal  without  either 
a  horny  or  a  stony  skeleton,  but  under  ordinary  conditions 
such  a  form  would  not  be  preserved. 

The  skeleton  of  a  primitive  hydroid,  Corynoides  calicu- 
laris  Nich.  (No.  99 ;  PI.  100,  drawing  of  the  same  en- 
larged), is  found  as  a  fossil  in  the  ancient  geological 
formations.  It  was  tubular  in  form,  chitinous  in  structure, 
and  striated  on  the  outside  as  shown  in  the  figure.  The 
body  of  the  aclult,  one  may  infer  from  the  skeleton,  was 
tubular  with  an  opening  or  mouth  at  one  end  raised,  it  may 
be,  on  an  oral  cone,  the  base  of  which  may  or  may  not 
have  been  surrounded  by  tentacles.  This  mouth  probably 
led  into  a  hollow  body  cavity.  The  basal  portion  of  the 
tubular  skeleton  ended  in  two  little  spines,  but  there  is  no 
indication  in  the  fossils  that  the  animal  was  attached,  and 
therefore  the  conclusion  may  be  drawn  that  it  was  free- 
moving  both  in  youth  and  in  adult  life. 

Nothing  is  known  of  the  development  of  this  ancient 
hydroid,  but  the  simplicity  of  its  structure  as  shown  by  its 
skeleton  leads  to  the  natural  supposition  that  the  develop- 
ment was  primitive ;  that  is,  without  a  metamorphosis  of 
any  kind. 

The  descendants  of  this  single  marine  form  may  have 
budded,  and  if  the  new  zoons  remained  together  a  free- 
moving  colony  would  arise  similar  in  some  respects  to 
Graptolites  (Nos.  101-104). 

According  to  Lapworth,1  who  has  studied  the  develop- 
ment of  the  Graptolitidae,  the  colonies  arise  from  a  "  small, 
pointed,  triangular  or  rather  dagger-like  'germ',"  which 
he  calls  the  sicula.  It  may  be  that  this  youthful  stage  is 
the  representative  of  the  single,  ancestral  Corynoides,  al- 
though this  is  not  proved.  In  time  a  solid  axis  or  virgu- 
la  develops  in  the  outer  wall  of  the  sicula  and  often  extends 
beyond  it  at  either  end.  A  small  bud  usually  appears  at 

.  Mag.,  London,  X,  1873. 


METAZOA —  COELENTERA.  91 

the  larger  end  and  this  forms  a  protecting  cup  or  theca. 
While  this  is  the  rule,  there  are  genera  in  which  the  bud 
arises  from  the  middle  portion  of  the  sicula  and  from  the 
smaller  end.  As  a  general  thing  the  sicula  is  retained 
unchanged  in  form  by  the  mature  animal,  but  in  a  few 
species  it  is  absorbed  or  becomes  obsolete  in  old  age. 

The  group  of  Monograptidae  is  represented  by  Mono- 
graptus  (No.  101),  which  has  a  single  series  of  cups  or 
thecae  on  one  side  and  at  their  base  a  well  developed 
virgula. 

Wiman l  has  made  a  study  of  the  Diplograptidae 
which  are  represented  in  the  Collection  by  Diplograptus 
(No.  102).  He  finds  that  these  forms  arise  in  the  same 
way  as  the  Monograptidae,  and  it  seems  probable  that 
they  are  the  specialized  descendants  of  the  last  named 
group.  The  sicula  of  Diplograptus  (PI.  103,  fig.  i, 
young,  dorsal  view;  fig.  2,  adult,  front  view)  consists  of 
two  parts :  the  proximal  portion  marked  diagonally ;  the 
distal,  longitudinally  (seen  in  fig.  i).  The  sicula  is  open 
at  its  base,  and  at  one  side  is  the  rod  or  virgula.  This 
sicula  gives  forth  one  bud  only,  which  does  not  develop 
into  a  canal  as  heretofore  supposed,  but  into  a  cup  or 
theca.  Fig.  3  is  a  front  view  of  the  first  theca  budded 
from  the  sicula,  and  fig.  4  is  a  dorsal  view  of  the  same. 

The  circular  perforation  in  fig.  3  marks  its  origin  from 
the  sicula.  The  theca  grows  downward,  then  outward. 
Fig.  5  is  the  first  theca  with  three  spines,  two  of  which 
are  united  by  a  thin  skin.  The  theca  is  seen  to  have 
grown  outward  and  upward.  In  time  this  theca  buds  and 
the  second  theca  grows  around  to  the  opposite  side.  This 
process  is  repeated,  the  second  giving  rise  to  the  third,  the 
third  to  the  fourth,  so  that  the  statement  can  be  made  that 
each  theca  comes  from  the  next  more  proximally  situated 
theca  of  the  opposite  side  and  not  from  a  canal.  Fig.  6 

1  Journ.  of  Geol.,  II,  no.  3,  Apr.-May,  1894,  p.  267.  See  also 
Holm,  Geol.  Mag.,  London,  Decade  IV,  II,  1895. 


92  SYNOPTIC    COLLECTION. 

is  a  front  view  showing  especially  the  form  and  position 
of  the  second  and  third  thecae,  and  fig.  7  shows  four  thecae 
and  the  partly  imbedded  sicula.  In  fig.  8  it  is  seen  how 
the  thecae  extend  more  and  more  over  the  sicula  until  the 
latter  becomes  incorporated  in  the  main  mass  or  hydro- 
zoma.  At  this  time  the  distal  end  of  the  virgula  begins 
to  grow,  and  it  becomes  stouter  the  farther  it  gets  from 
the  point  of  the  sicula.  In  fig.  9  the  distal  end  only  of  a 
hydrozoma  is  drawn,  the  proximal  end  with  its  imbedded 
sicula  not  being  represented. 

It  is  interesting  to  note  that  Ruedemann  J  has  shown 
that  some  species  of  Diplograptus  occur  in  large  compound 
colonies  consisting  of  many  branches  or  stipes  united  in 
the  center  as  seen  in  PI.  104.  These  hydroids  probably 
consisted  of  nutritive  zoons  possessing  tentacles  for  catch- 
ing food  and  cavities  for  digesting  it.  Besides  these  there 
were  doubtless  other  zoons  which  were  reproductive  in 
function.  The  latter  in  the  more  specialized  forms  may 
have  freed  themselves  from  the  colony  and  swum  away 
as  independent  organisms  or  medusae.  That  medusae 
lived  as  far  back  as  the  lower  Cambrian  has  been  proved 
by  Walcott. 2  As  we  come  down  to  the  present  time  we 
find  the  probable  representatives  of  the  Graptolites  in 
the  Plumularian  hydroids,  Aglaophenia  (No.  105)  and 
Sertularia  (No.  106;  no.  107,  dried  specimen).  The 
former  has  the  thecae  on  one  side  of  each  branch,  while 
Sertularia  has  them  on  both  sides.  These  hydroids  have 
reduced  characters,  since  the  reproductive  buds  or  gono- 
phores,  which  in  a  progressive  form  swim  away  as  free 
medusae,  here  never  become  detached.  These  are  finely 
shown  in  Sertularia  argentea  Ellis  and  Sol.  (No.  106). 


!Rep.  State  Geol.  N.  Y.,  1894,  p.  219. 
2U.  S.  Geol.  Surv.,  Monograph,  XXX,  li 


METAZOA —  COELENTERA.  93 


HYDROPHORA.  —  HYDROCORALLINAE. 

The  position  of  the  Hydrocorallinae  in  a  natural  classi- 
fication has  not  been  determined  with  certainty, l  but  they 
are  placed  here  provisionally. 

Millepora  is  a  colonial  form  which  secretes  a  calcareous 
skeleton  (No.  108).  The  zoons  occur  in  groups  (PI.  109, 
fig.  i),  each  group  consisting  of  a  short  central  zoon  and 
six  or  eight  long  ones  about  it ;  in  fig.  i  one  of  the  latter 
is  omitted  for  the  sake  of  clearness.  The  central  zoon, 
called  the  gastrozooid,  possesses  a  mouth  and  four  or 
more  tentacles,  while  the  surrounding  dactylozooids  are 
mouthless.  The  body  cavities  of  these  zoons  are  not  di- 
vided by  partitions,  but  are  continuous  into  the  canals 
which  traverse  the  surrounding  flesh  or  coenosarc  in  every 
direction. 

The  dactylozooids  apparently  catch  the  food  and  carry 
it  to  the  gastrozooid,  and  are  therefore  tentacular  in  func- 
tion while  they  bear  numerous  small  tentacles  on  their 
sides.  One  of  these  is  represented  in  fig.  2,  much  enlarged. 
Figs.  3  and  4  represent  a  nematocyst  taken  from  the  ten- 
tacles; these  are  like  those  of  most  hydroids.  Fig.  3  repre- 
sents the  thread  within  the  cell  and  fig.  4  shows  it  thrown 
out.  Besides  this  kind  of  thread  cell  there  is  another  in 
Millepora  found  near  the  bases  of  the  zoons  and  shown 
in  figs.  5  and  6.  Fig.  7  is  a  cross  section  of  a  gastrozooid 
showing  on  the  outside  the  ectoderm  nematocysts  in  dif- 
ferent stages  of  development.  Inside  are  the  large  trans- 
parent cells  which  are  called  gastric  because  they  occur 
only  in  the  gastrozooid  and  therefore  may  be  digestive  in 
function.  The  muscles  by  which  the  zoons  contract  are 
shown  in  fig.  8  which  is  a  diagram  of  the  longitudinal 

1  For  a  discussion  of  the  different  views  on  the  subject,  see  Moseley, 
Chall.  Rep.,  Zoo!.,  II,  part  7,  1881,  p.  98;  also  Hickson,  Quart. 
Journ.  Micr.  Sci.,  XXXII,  1891^.375;  Proc.  Zool.  Soc.  London, 
1898,  p.  246. 


94  SYNOPTIC    COLLECTION. 

bundles  of  fibers  that  arise  from  the  radiating  vessels, 
the  latter  being  the  continuations  of  the  body  cavities  of 
the  zoons.  Besides  the  longitudinal  muscles  the  circular 
muscles  are  shown.  Fig.  9  is  a  vertical  section  through 
the  decalcified  superficial  fleshy  lamina  which  was  living 
before  decalcification  began ;  the  ectoderm  is  distinctly 
seen,  also  the  retracted  gastrozooids  on  the  right  (one 
of  the  four  tentacles  is  not  drawn) ,  and  the  retracted 
dactylozooid  on  the  left.  The  network  of  fleshy  tubes  is 
finely  seen  and  where  these  are  cut  the  dark  pigment  cells 
of  the  endoderm  are  visible.  The  limy  network  of  the 
skeleton  is  shown  by  the  open  spaces  between  the  fleshy 
tubes.  Figs.  10-15  represent  the  skeleton.  Fig.  10  is 
a  fragment  magnified  two  diameters,  showing  the  branch- 
ing form  and  the  pores  scattered  over  the  surface.  Fig. 
1 1  is  a  drawing  of  a  thin  section  of  the  skeleton  showing 
its  nbro-crystalline  structure.  Fig.  12  is  a  complete  group 
of  pores  consisting  of  one  central  gastrozooid  pore  and 
eight  dactylozooid  pores,  greatly  enlarged.  The  structure 
is  brought  out  clearly  by  figs.  13-15.  Fig.  13  is  a  verti- 
cal section  of  the  skeleton.  The  large  gastrozooid  pore 
is  seen  in  the  middle  and  the  floor  that  separated  the  last 
formed  living  chamber  from  those  below  which  are  dead. 
The  branches  of  the  canal  system  are  plainly  shown.  Fig. 
14  is  a  horizontal  section  cut  parallel  to  the  outer  surface, 
showing  part  of  a  group  and  the  system  of  canals.  In 
fig.  15  the  pores  and  canals  have  become  filled  with  black 
foreign  matter  making  a  cast  of  the  canal  system  of  the 
flesh  or  coenosarc.  Nothing  was  known  of  the  generative 
organs  of  Millepora  till  1884,  when  Quelch  l  found  among 
the  young  branchlets  of  the  hard  skeleton  large  ampulla- 
like  cavities  similar  to  those  that  had  previously  been 
observed  in  a  related  group,  the  Stylasteridae.  These 
cavities  contained  gonophores  and  in  the  specimen  exam- 
ined only  the  male  elements,  spermatozoa,  were  found. 

i  Nature,  XXX,  1884,  p.  539. 


METAZOA COELENTERA.  95 

In  1886,  Hickson1  observed  that  the  generative  prod- 
ucts of  Millepora  were  formed  in  little  capsules  in  the 
walls  of  the  canals  and  that  both  male  and  female  cap- 
sules were  found  in  the  same  canals.  This  author  has 
also  described  and  figured2  the  medusae  of  Millepora. 
These  are  formed  by  a  metamorphosis  of  an  ordinary 
zoon,  usually  a  dactylozooid  but  sometimes  a  gastrozooid. 
They  occur  in  ampulla-like  cavities  of  the  coenosarc. 
When  they  leave  the  parent  form  they  are  without  the 
radial  or  ring  canals,  veil  (velum),  and  sensory  organs 
common  to  the  more  specialized  medusae.  It  may  be 
that  these  develop  later  while  the  animal  swims  about  in 
the  water,  or  it  may  be  the  medusae  remain  in  a  primitive 
condition. 

PI.  no,  fig.  i,  is  a  section  through  a  medusa  of  Mille- 
pora murrayi.  It  has  a  well  developed  manubrium  (the 
part  hanging  down  like  a  handle),  containing  a  cavity 
continuous  with  a  large  canal  of  the  parent  stock;  the 
rounded  masses  on  either  side  of  the  manubrium  repre- 
sent the  sperm,  and  the  outer  encircling  portion  the  um- 
brella. The  ectodermal  parts  are  shaded  pink  and  the 
endodermal  blue.  Fig.  2  is  a  section  of  an  older  medusa 
that  is  not  organically  connected  with  the  colony  at  any 
point  and  is  probably  ready  to  escape. 

Distichopora  (No.  in)  has  a  beautiful  pink  skeleton. 
The  openings  are  not  in  groups  as  in  Millepora,  but  are 
either  in  rows  along  the  edges  of  the  branches  or  arranged 
in  wavy  lines  over  the  surface.  The  rows  of  pores  con- 
sist of  a  middle  row  of  gastrozooids  with  dactylozooids  on 
either  side.  The  ampulla-like  cavities  in  this  genus  are 
on  one  or  both  faces  of  the  branch.  The  gonophores  are 
not  metamorphosed  dactylozooids,  becoming  free-swim- 
ming medusae,  but  are  modifications  of  the  ova  and  sperm 
cells  in  the  canals  of  the  coenosarc  which  never  become 
detached. 


!Proc.  Roy.  Soc.  London,  XL,  1886,  p.  325. 
2  Quart.  Journ.  Micr.  Sci.,  XXXII,  1891,  p.  375. 


SYNOPTIC    COLLECTION. 


H  YDROPHORA. NARCOMEDUSAE. 

The  Narcomedusae  are  a  group  of  living  hydroids 
which  throw  considerable  light  on  the  evolutionary  history 
of  the  Hydrozoa,  as  pointed  out  by  Brooks.1  PL  112, 
figs.  1-19,  represents  the  development  of  Aeginopsis 
from  the  egg  to  the  hydra  stage.  Fig.  i  is  the  fresh  laid 
egg;  fig.  2,  the  two  celled  stage;  fig.  3,  the  beginning  of 
the  second  furrowing  stage  ;  fig.  4,  the  four  celled  stage  ; 
fig.  5,  the  beginning  of  the  third  furrowing  stage;  fig.  6, 
the  eight  celled  stage;  and  .fig.  7,  the  beginning  of  the 
fourth  furrowing  stage  ;  fig.  8  is  the  sixteen  celled  embryo 
in  cross  section;  fig.  9,  the  embryo  composed  of  about 
thirty-two  cells.  Figs.  10  and  1 1  show  isolated  cells  of  the 
same  embryo;  fig.  10  is  the  endoderm  cell  just  formed, 
and  fig.  ii,  the  completed  or  finished  endoderm  cell. 
Fig.  12  is  the  embryo  of  fifty-nine  cells ;  fig.  13  is  the  two 
layered  larva;  fig.  14,  the  larva  lengthened;  fig.  15,  the 
further  developed  larva;  figs.  16  and  17,  cells  of  the  same 
(16,  cell  of  ectoderm;  17,  of  endoderm)  ;  fig.  18  is  the 
larva  with  two  tentacles  and  no  mouth;  fig.  19,  the  larva 
of  the  fourth  day.  It  is  now  a  hydra  witji  a  shortened 
body,  a  mouth  at  the  end  of  a  long  oral  cone,  at  the  base 
of  which  are  tentacles.  Unfortunately  Metschnikoff  did 
not  figure  the  further  development  of  the  hydra  into  the 
medusa.  The  tentacular  zone,  however,  grows  out  into 
an  umbrella  which  carries  the  tentacles  with  it;  sense 
organs  and  a  veil  or  velum  are  soon  acquired,  and  the 
hydra  becomes  converted  into  a  medusa.  Its  parts  can 
be  plainly  traced  in  the  medusa,  and  the  difference  in 
external  appearance  is  due  mainly  to  the  great  develop- 
ment of  the  middle  layer  or  mesoderm  which  forms  the 
umbrella.  If  now  we  could  find  a  genus  where  the  larva, 
while  yet  a  hydra,  should  fasten  itself  to  some  object, 

iMem.  Boston  Soc.  Nat.  Hist.,  Ill,  no.  -12,  1886. 


METAZOA COELENTERA.  97 

either  an  animal  or  a  rock,  and  should  bud,  then  a  colony 
would  arise.  This  is  precisely  the  case  with  Cunocantha 
(  —  Cunoctantha^}  octonaria  Hkl.,  or  Cunina  octonaria 
McGrady,  the  latter  name  being  the  more  familiar  one. 
PI.  113  gives  the  development  of  this  genus,  and  No.  114 
is  the  medusa  of  Cunina  campanulata  Ed.  PI.  113,  fig.  i, 
is  the  larva.  (Figs,  i  and  3  are  drawn  in  a  position  to 
show  the  hydra-like  larva;  fig.  5,  to  show  the  medusa-like 
adult.)  The  aboral  end  of  the  body  is  shortened;  there 
are  two  opposite  tentacles  which  have  clusters  of  thread 
cells  at  their  ends.  The  oral  cone  which  extends  above 
is  very  long  and  at  its  end  is  the  small  mouth.  The 
internal  cavity  is  lined  with  large  endodermal  cells  seen 
in  the  figure.  The  ectoderm  is  thin  excepting  at  the 
extremities  of  the  tentacles  and  at  the  aboral  end  of  the 
body.  This  larva  now  enters  the  bell  cavity  of  Turritop- 
sis,  another  Hydrozoan,  and  fastens  itself  by  its  tentacles, 
as  seen  in  fig.  2.  The  oral  cone  becomes  extremely  long, 
is  inserted  in  the  mouth  of  Turritopsis,  and  two  more 
tentacles  grow.  This  stage  is  more  clearly  seen  in  fig.  3. 
Either  before  or  after  the  secondary  tentacles  appear,  the 
hydra  puts  forth  buds  from  the  aboral  end  of  the  body 
and  a  colony  is  formed  as  seen  in  figs.  4  and  5.  A  rim 
grows  out  from  the  body  in  the  tentacular  zone  and  this 
rim  becomes  divided  into  eight  lobes,  each  one  of  which 
contains  a  branch  from  the  central  digestive  cavity.  The 
bud,  thus  changed,  escapes  into  the  water  and  is  a  medusa 
(PI.  1 13,  fig.  6)  with  a  long  oral  cone.  Later  the  umbrella 
enlarges  while  the  oral  cone  remains  about  the  same  as 
seen  in  fig.  7,  which  is  an  aboral  view  of  an  adult  medusa. 
Each  member  of  the  colony  becomes  converted  into  a 
medusa,  so  that  here  we  have  budding  and  a  primitive 
kind  of  metamorphosis  but  no  alternation  of  generations. 
The  Cunina  parasitica,  however,  which  attaches  itself 

1  H.  V.  Wilson,  Stud.  Biol.  Lab.  Johns  Hopkins  Univ.,  IV,  no. 
2,  1887,  p.  95. 


98  SYNOPTIC    COLLECTION. 

to  one  of  the  Geryonids,  remains  a  hydra,  while  its  buds 
develop  into  medusae  and  swim  away.  Here,  then,  we 
have  the  metamorphosis  of  Aeginopsis  converted  into  the 
alternation  of  generations  so  peculiar  to  this  class  of  ani- 
mals. 

The  objection  may  here  be  urged  that  the  genus  Cunina 
is  parasitic  or  semi-parasitic  in  habit  and  that  therefore  it 
is  a  specialized  and  reduced  genus.  The  stock  form 
Aeginopsis,  which  is  the  key  to  our  classification,  is  not 
a  parasite  at  any  period  of  life.  Cunina  octonaria  does 
not  seem  to  be  much  more  of  a  parasite  than  an  animal 
that  happens  to  settle  upon  something,  it  may  be  another 
animal  or  a  rock,  for  a  short  time.  It  is  free  at  first,  then 
attaches  itself  to  an  animal  for  a  brief  period,  and  after- 
ward lives  an  independent  life.  The  species  Cunina  par- 
asitica  is  a  parasite,  as  its  name  implies,  but  it  illustrates 
so  admirably  what  seems  to  us  the  next  step  in  the  evolu- 
tionary development  of  this  class  of  animals  that  we  use 
it  provisionally,  until  at  least  a  non-parasitic  form  can  be 
found  which  will  illustrate  the  same  type  of  life  history. 

HYDROPHORA. —  TRACHOMEDUSAE. 

The  Trachomedusae  are  represented  in  the  Collection 
by  Carmarina  (  =  Geryonia)  hastatalAld.  (No.  115),  which 
corresponds  to  Aeginopsis  among  the  Narcomedusae  in 
passing  through  a  metamorphosis  without  budding  or 
alternation  of  generations.  It  is  an  interesting  fact  that 
the  larval  Geryonidae  have  solid  tentacles,  while  in  the 
adults  these  are  replaced  by  hollow  ones.  The  Tracho- 
medusae include  Aglaura  whose  complete  development 
has  been  worked  out  by  Metschnikoff.  PL  116,  fig.  i  is 
the  fresh  laid  egg  drawn  from  life;  fig.  2,  the  same  treated 
with  osmic  acid  ;  fig.  3  shows  the  beginning  of  .segmenta- 
tion;  fig.  4.  the  egg  divided  into  two  cells;  fig.  5,  the 
four  celled  stage ;  fig.  6  is  the  third  furrowing  stage  from 


METAZOA —  COELENTERA.  99 

above;  fig.  7,  the  same  in  profile;  fig.  8  is  the  beginning 
of  the  fourth  furrowing  stage ;  fig.  9,  the  same  a  half  hour 
afterward  ;  fig.  10,  the  same  three  quarters  of  an  hour  after 
fig.  8.  The  rotating  movements  of  the  embryo  begin  at 
tfns  time.  Figs,  n  and  12  are  further  developed  stages; 
fig.  13  is  the  morula  stage;  fig.  14,  the  larva  with  two 
layers;  figs.  15  and  16  are  the  free-swimming  larvae; 
fig.  17  is  the  larva  with  nettle  capsule ;  fig.  18,  a  further 
developed  larva;  fig.  19,  a  larva  with  projecting  tentacles  ; 
fig.  20,  larva  with  gastro-vascular  cavity.;  fig.  21  shows 
the  beginnings  of  the  wider  tentacles;  fig.  22  is  a  larva 
forty-five  hours  old,  and  fig.  23,  one  fifty-two  hours  old; 
fig.  24  is  a  larva  with  eight  tentacles,  and  fig.  25,  one 
with  twelve  tentacles;  fig.  26  is  the  same  in  profile,  and 
fig.  27,  the  disc  of  same  from  above.  Fig.  28  is  the  adult 
Aglaura. 

In  some  of  the  most  specialized  genera  of  the  Tracho- 
medusae  there  are  various  secondary  modifications,  and 
the  adult  characteristic  of  a  peculiar  bell-shaped  body 
appears  in  the  young. 


HYDROPHORA.  —  ANTHOMEDUSAE. 

Acaulis  (PI.  117,  figs.  1—3)  may  be  one  of  the  primi- 
tive forms  of  the  Anthomedusae,  although  as  yet  it  is  not 
positively  known  that  the  medusae  become  free.  Fig. 

1  represents  a  portion  of  a  young  Acaulis.     The  blunt 
posterior  end  is  shown  with  both  the  temporary  tentacles, 
which  are  short  and  swollen  at  their  ends,  and  the  perma- 
nent ones  which  are  long  and  slender  throughout.     Figs. 

2  and  3  probably  represent  the  adult,  one  much  enlarged, 
the  other  natural  size.     The  mouth  is  at  the  smaller  end 
with  numerous  papillae  about  it ;  the  temporary  tentacles 
of  the  young  have  disappeared.     Below  the  papillae  are 
the  clusters  of  gonophores  which  Stimpson  observed  "in 
an  advanced  stage  of  development,  soon  to  become  free- 


100  SYNOPTIC    COLLECTION. 

swimming  individuals."  The  adult  Acaulis  (figs.  2,  3)  is 
attached  by  its  base. 

Among  the  Tubularians  there  are  some  species  which 
develop  free  medusae,  while  others  are  more  or  less 
reduced.  In  this  group  the  zoons  are  at  the  ends  of  long 
tubes,  and  those  with  the  reproductive  function  are  some- 
times in  the  form  of  clusters  of  grapes. 

Corymorpha  nutans  Sars  (No.  118),  is  a  solitary  Tubu- 
larian.  The  natural  size  is  represented  at  the  left,  while 
just  back  of  it -is  the  same  greatly  enlarged.  At  its  base 
are  many  thread-like  organs  for  anchoring  the  animal  in 
the  sand.  A  number  of  short  tentacles  are  seen  around 
the  mouth,  and  farther  down  there  is  another  circlet  of 
much  longer  feelers.  Between  these  two  sets  of  tentacles 
are  the  medusae  buds.  These  have  only  one  tentacle 
when  young  and  attached  and  also  when  mature  and  free 
(No.  118,  at  the  right).  This  model  clearly  shows  the 
four  radiating  canals  and  the  manubrium. 

In  Turritopsis  (No.  119)  we  have  a  greater  complexity 
of  the  hydroid  stage  than  that  previously  described.  The 
free-swimming  embryo  does  not  grow  into  a  hydra,  but, 
spreading  out  more  or  less  like  a  root,  attaches  itself  and 
buds  forth  hydras.  In  .this  way  a  colony  arises.  The 
hydras  in  their  turn  bud  medusae  which  swim  away. 
Here  we  have  a  modification  of  the  phenomenon  of  alter- 
nation of  generations  and  a  root-like  form  existing  between 
the  parenchymella  and  the  hydroid  stage. 

The  life  history  of  Podocoryne  is  especially  interesting. 
It  begins  its  existence  as  a  hydroid,  then  forms  a  colony 
by  budding,  and  puts  forth  secondary  buds  in  the  form 
of  medusae.  These  swim  away,  but  after  a  time  they 
take  on  reduced  characters.  The  veil  disappears,  the  bell 
is  reversed,  shrunken  to  a  shapeless  mass,  and  turned 
back  with  the  tentacles  (PI.  120).  The  eggs  are  seen  in 
the  walls  of  the  manubrium  which  hangs  down  below  the 
shrunken  bell. 

This  figure  is  instructive   as  showing  the  difference 


METAZOA COELENTERA.  101 

between  a  reduced  and  a  primitive  form.  While  resem- 
bling each  other  in  a  general  way,  close  examination 
reveals  here,  as  in  the  great  majority  of  cases,  the  evolu- 
tionary stages  through  which  the  hydroid  has  passed. 

Cladonema  (No.  121)  is  another  Tubularian  which 
illustrates  suppressed  development.  The  model  repre- 
sents the  hydroid  of  natural  size  (a)  and  enlarged  (b)  ;  c 
and  d  are  the  young  and  the  adult  medusae.  When  old, 
the  medusa  tends  to  lose  its  umbrella  and  takes  on  other 
reduced  characters. 

Tubularia  larynx  E.  &  S.  (No.  122),  is  one  of  our 
common  hydroids  and  is  a  good  example  of  suppressed 
development.  The  zoons  rise  from  basal  stolons  which 
form  a  network  and  grow  to  the  height  of  four  or  five 
inches.  The  network  and  ascending  tubes  are  protected 
by  a  chitinous  sheath,  but  this  does  not  cover  the  main 
body  of  the  zoon,  often  called  the  hydranth.  Each 
hydranth  has  a  double  row  of  tentacles.  Below  these  on 
the  reproductive  zoons  are  the  grape-like  clusters  of 
medusae  which  never  become  detached. 

The  scarlet  colored  masses  of  Clava  (No.  123)  are 
abundant  on  the  New  England  coast.  The  larval  hydra 
becomes  attached  and  forms  a  colony  like  the  parent. 
The  model  represents  the  nutritive  zoons  with  many  ten- 
tacles, and  the  reproductive  zoons  are  in  clusters  beneath  ; 
as  these  are  medusae  which  never  become  free,  we  have 
here  another  illustration  of  suppressed  development. 


HYDROPHORA. —  HYDROIDEA. 

The  fresh-water  Microhydra  ryderi  Potts,1  is  described 
here  since  it  produces  free-swimming  medusae2,  which, 

1Amer.    Nat,   XIX,   1885,  p.    1232.     Quart.  Journ.  Micr.   Sci. 
XXX,  1890,  p.  507." 

2  Potts,  Amer.  Nat.,  XXXI,  1897,  p.  1032. 


102  SYNOPTIC    COLLECTION. 

so  far  as  our  knowledge  goes,  is  not  true  of  Protohydra 
or  Hydra.  In  the  hydro  id  state  Microhydra  is  greatly 
reduced,  since  it  possesses  neither  chitinous  coat  nor  ten- 
tacles, and  is  also  without  a  pedal  disc.  According  to 
Potts  this  species  was  found  living  as  a  messmate  among 
colonies  of  Bryozoa  "  where  its  own  disabilities  as  a  food 
collector  ....  were  supplemented  by  the  life  sustaining 
currents  induced  by  its  more  active  neighbors."  This 
habit  has  doubtless  brought  about  this  reduced  structural 
condition. 

The  marine  and  fresh-water  Protohydra  of  Greef  is  rep- 
resented by  Pis.  124  and  125.  It  is  less  reduced  than 
Microhydra,  by  possessing  a  chitinous  coat  and  by  living 
in  both  salt  and  fresh  water,  but,  like  this  genus,  it  is  with- 
out tentacles.  PI.  124,  fig.  i  represents  Protohydra  con- 
tracted into  a  spherical  form.  Its  color  is  a  fox  brown. 
Fig.  2  shows  the  little  animal  in  the  act  of  stretching  out, 
and  in  figs.  3  and  4  it  is  still  more  extended.  In  the  lat- 
ter figure  the  mouth  is  seen  at  the  top  and  the  foot  disc 
at  the  posterior  end.  Fig.  5  is  a  Protohydra  that  has 
swallowed  a  Copepod  larger  than  its  own  body.  The  long 
bristles  at  the  posterior  end  of  the  crustacean  extend  from 
the  mouth.  Inside  the  hydroid  the  outlines  of  the  Cope- 
pod  can  be  made  out  and  also  one  of  its  red  eyes.  Fig. 
6  is  the  forward  end  enlarged,  showing  the  edges  of  the 
mouth  without  even  the  vestiges  of  tentacles.  Fig.  7  is  a 
portion  of  the  body  showing  the  network  of  cells.  In 
these  figures  the  nearly  colorless  ectoderm  is  seen  and  the 
underlying  pigmented  endoderm :  no  cuticle  is  repre- 
sented excepting  in  fig.  8  (which  is  the  posterior  part  of 
a  specimen  that  has  been  paralyzed  in  fresh  water)  where 
it  is  visible  outside  of  the  cellular  ectoderm.  According 
to  Greef1  this  is  most  constant  at  the  end  of  the  body 
where  it  has  separated  from  the  epithelium  and  surrounds 
the  body  like  a  tube.  Towards  the  forward  end  it  lies 

1  Zeitschr.  f.  wiss.  Zool.,  XX,  p.  1070. 


METAZOA COELENTERA.  103 

so  close  to  the  surface  that  one  may  doubt  its  existence. 
Singularly  enough  Protohydra  increases  by  cross  division. 
PI.  125,  fig.  i  shows  the  beginning  of  the  process.  The 
constriction  goes  on  until  the  two  are  nearly  ready  to 
separate"  (figs.  2,3)  when  the  two  break  away  and  live 
independent  lives. 

This  process  of  reproduction  may  indicate  affinities 
with  the  Protozoa,  some  of  which,  as  we  have  seen, 
increase  by  transverse  division,  or  it  may  be  possible  that 
Protohydra  is  a  reduced  form  of  the  Discophora,  a  group 
which  multiplies  by  cross  division  with  alternation  of  gen- 
erations, and  one  which  will  be  described  farther  on. 

We  consider  Hydra  as  a  reduced  form  although  most 
of  the  books  place  it  as  a  primitive  hydroid.  Observa- 
tions1 have  shown  that  the  ectoderm  of  the  embryo  of 
Hydra  excretes  a  chitinous  coat.  This  is  probably  the 
vestige  of  the  horny  covering  or  exoskeleton  of  the  Tubu- 
larian  hydroids.  Later  this  sheath  is  thrown  off. 

We  have  already  seen  that  primitive  forms  are,  as  a 
rule,  marine,  and  the  Hydra  has  been  found  but  once  in 
brackish  "water,2  being  preeminently  a  fresh-water  animal. 
The  middle  layer  which  exists  under  varying  forms  in  the 
Coelentera  consists  in  the  Hydra  of  many  delicate  fila- 
ments extending  from  the  cells  of  the  ectoderm.  These 
may  represent  either  rudiments  or  vestiges  of  cells  and 
in  the  present  state  of  our  knowledge  it  is  impossible  to 
say  which  they  are  with  absolute  certainty.  It  would 
seem,  however,  from  observations  already  made,  that  they 
are  vestiges  and  that  we  are  not  dealing  here  with  a  prim- 
itive adult  two  layered*  animal,  whose  proper  taxonomic 
position  would  be  before  the  sponges,  but  rather  with  a 
modified  and  reduced  hydroid  form. 

1  See    Kleinenberg,    The    Hydra,    1872.      Huxley,    Anatomy   of 
Invertebrate  Animals,  1878,  p.  121.     Korotneff,  Embryology  of  the 
Hydra,    Zeitschr.    f.  wiss.    Zool.,    XXXVIII,    1883,    pp.    314-321. 
Brauer,  Zeitschr.  f.  wiss.  Zool.,  LII,  1891  ;    abstract,    Journ.    Roy. 
Micr.  Soc.,  1891,  p.  609  ;  also  Amer.  Nat.,  XXV,  1891,  p.  1027. 

2  Stand.  Nat.  Hist.,  I,  1885,  p.  77. 


104  SYNOPTIC    COLLECTION. 

The  adult  Hydra  (No.  126,  natural  size;  PI.  127, 
fig.  i)  has  a  tubular  body  with  a  mouth  at  the  end  of  an 
oral  cone.  At  the  base  of  the  latter  is  a  circle  of  tenta- 
cles. These  never  possess  the  primitive  character  of 
solidity  but  are  from  the  first  hollow  prolongations  of  the 
body  wall.  This  mature  form  buds  into  other  hydras 
(No.  126)  ;  it  also  reproduces  sexually.  PI.  127,  fig.. 2, 
represents  the  Hydra,  enlarged,  with  a  swelling  which  is  an 
ovum  or  egg,  and  nearer  the  tentacles  are  two  smaller 
swellings  that  are  sacs  containing  the  spermatozoa.  This 
animal  never  buds  a  medusa;  in  fact,  no  medusoid  char- 
acters have  been  observed  in  the  embryo,  and  for  this 
reason  some  naturalists  maintain  that  the  Hydra  cannot 
be  a  reduced  form.  The  difficulty  of  explaining  the  non- 
existence  of  medusoid  characters  in  the  young,  however, 
is  not  so  great  as  that  which  the  advocates  of  the  primi- 
tive character  of  Hydra  find  in  explaining  the  existence  of 
the  chitinous  sheath  in  the  embryo.  There  are  forms  in 
other  classes  of  the  animal  kingdom  which  have  become 
so  extremely  reduced  as  to  lose  even  in  their  embryo- 
logical  development  the  .characters  of  their  previously 
differentiated  condition,  and  it  seems  probable  that  the 
Hydra  can  be  numbered  among  these  forms. 


HYDROPHORA.  —  CAMPANULARIAE. 

The  Campanulariae  are  represented  by  Obelia  (No. 
128),  Tima  (No.  129),  Gonionemus  (No.  130),  and 
Gonothyraea  (No.  131  ;  PI.  132).  *  In  Obelia  we  have  a 
complicated  structure  and  life  history.  Its  egg  develops 
into  a  parenchymella  which  becomes  attached.  It  now 
forms  a  "star-shaped  root"  or  hydrorhiza  from  which  the 
first  zoon  is  budded ;  afterward  other  zoons  bud  out  from 
it  and  a  colony  is  produced.  Here,  as  in  Turritopsis  of 
the  Tubulariae,  we  have  a  precocious  embryo  and  an 
alternation  of  generations  between  the  parenchymella 
and  hydra  stages. 


METAZOA COELENTERA.  105 

The  hydras  budded  from  the  star-shaped  root  become 
differentiated  into  nutritive  and  reproductive  zoons,  the 
latter  giving  rise  to  medusa  buds.  These  medusae  are 
free  in  Obelia,  Tima,  and  Gonionemus  (No.  130,  show- 
ing young  stages),  but  in  Gonothyraea  (No.  131  ;  PI.  132, 
enlarged)  they  are  reduced  and  always  remain  attached. 


DISCOPHORA. 

We  have  shown  that  the  complex  larval  colonies  and 
specialized  adults  of  the  Hydrophora  may  have  arisen 
from  the  comparatively  simple  Aeginopsis.  It  may  be 
possible  also  that  this  same  form,  or  one  similar  to  it, 
produced  along  another  line  of  development  the  Disco- 
phora.  The  egg  of  most  Discophora,  like  that  of  Aegi- 
nopsis, develops  into  a  free-swimming,  ciliated,  solid 
embryo  or  parenchymella.  This  attaches  itself  and  in 
time  becomes  a  hydra.  By  a  remarkable  growth  the 
height  increases  greatly.  The  body  then  begins  to  divide 
horizontally,  and  the  saucer-like  divisions  free  themselves 
as  medusae.  Thus  it  is  seen  that  one  hydra  gives  rise  by 
the  process  of  division  to  several  medusae.  The  latter 
produce  eggs  which  develop  into  the  hydra  form,  so  that 
we  have  an  asexual  hydroid  generation  alternating  with 
a  sexual  medusa  generation.  The  Discophora  are  repre- 
sented in  the  Collection  by  Cyanea  capillata  Linn.  (No. 
133,  greatly  reduced),  Aurelia  flavidula  Per.  &  Less. 
(PI.  134),  and  Aurelia  aurita  Lirwi.  (No.  135,  young 
medusa;  No.  136,  adult).  It  is  interesting  to  note  that 
the  adult  medusa  of  Cyanea  sometimes  attaches  itself 
quite  firmly  to  an  object.  One  observed  by  Dr.  Robert 
T.  Jackson,  at  Eastport,  Maine,  in  the  summer  of  1892, 
was  settled  so  firmly  that  it  required  considerable  force 
to  separate  it  from  the  tub  in  which  it  was  living.  While 
attached,  its  resemblance  to  a  hydra  was  striking. 

The  segmentation  of  the  egg  of  Cyanea  is  regular  and 


106  SYNOPTIC    COLLECTION. 

results  in  the  formation  of  a  blastula.  Cells  then  migrate 
into  the  interior  and  afterward  arrange  themselves  as  an 
incomplete  layer  on  the  inner  side.  Here,  then,  in  Cyanea 
we  have  the  stage  following  the  blastula  produced  by  the 
immigration  of  cells  and  not  by  the  invagination  of  a  layer. 
The  parenchymella,  after  swimming  about  freely,  settles 
down  and  forms  a  cyst.  Soon  after  leaving  the  cyst  a 
mouth  opens  and  four  tentacles  are  developed.1 

The  development  of  Aurelia  illustrates  that  of  most 
Discophora.  PI.  134,  fig.  i,  represents  one  of  the  early 
stages  of  the  egg,  and  fig.  2,  the  fully  grown  egg.  Seg- 
mentation takes  place  and  when  the  embryo  leaves  the 
parent  it  swims  about  by  means  of  cilia  (fig.  3).  Grad- 
ually the  two  layers  are  formed  (fig.  4) ,  then  the  digestive 
cavity  (fig.  5).  Afterward  a  depression  in  the  outer  sur- 
face of  the  inner  wall  marks  the  position  of  the  future 
mouth  (fig.  6) ;  in  time  the  outer  wall  is  pierced  and  the 
mouth  and  passage  leading  to  the  digestive  cavity  appear. 
The  embryo  becomes  elongated  (fig.  7) .  It  now  gives  up 
its  free  life.  According  to  Prof.  Louis  Agassiz,  "  it  settles 
down  upon  its  narrow  end  ;  it  wavers,  and  sways  to  and 
fro  as  if  it  were  trying  to  force  its  way  downward  into  the 
substance  upon  which  it  has  fastened  itself,  and  then,  as 
if  dissatisfied  with  the  promise  of  a  good  basis  for  its  foun- 
dation, it  suddenly  loosens  its  hold  and  swims  away  to 
another  locality,  there  to  repeat  the  same  kind  of  examina- 
tion until  finally,  after  perhaps  half  a  dozen  attempts  ....  it 
finds  a  suitable  place  to  rest  upon  permanently."  The 
changes  which  take  place  at  this  time  are  more  clearly 
seen  in  figs.  8-n  which  are  taken  from  the  development 
of  Cyanea  already  briefly  described.  Fig.  8  represents 
the  embryo  with  a  chitinous  base  which  serves  to 
strengthen  its  attachment.  In  fig.  9  the  two  tentacles 
are  just  beginning  to  grow.  Fig.  10  has  four  tentacles 
(well  provided  with  thread  cells)  and  a  wide  opened 

1See  Smith,  Bull.  Mus.  Comp.  Zool.,  XXII,  1891,  p.  124. 


METAZOA  —  COELENTER A.  107 

mouth.  Fig.  1 1  is  a  so  called  scyphostoma  with  four 
tentacles  extended,  surrounding  a  mouth  at  the  end  of  an 
ora'l  cone. 

It  is  interesting  to  note  that  the  scyphostoma  of  Cyanea 
has  a  horny  sheath  similar  to  that  possessed  by  the  Tubu- 
lariae.  No  such  sheath  has  been  observed  in  Aurelia. 
One  feature  of  the  anatomy  of  the  scyphostoma  is  of  im- 
portance. Four  ridges  extend  from  the  inner  wall  into 
the  central  cavity  and  divide  its  outer  portion  into  four 
chambers.  These  are  probably  the  beginnings  of  the 
mesenteries  of  the  Anthozoa. 

The  scyphostoma  of  Aurelia  (fig.  12)  normally  develops 
sixteen  tentacles.  It  is  converted  into  the  so  called  stro- 
bila  in  the  following  way.  A  horizontal  constriction  takes 
place  just  below  the  outer  base  of  the  tentacles  (fig.  13)  ; 
this  is  followed  by  another  (fig.  14),  and  a  third  (fig.  15), 
and  still  others,  until  nearly  the  whole  body  is  divided 
into  saucer-like  sections.  At  the  base  of  these  sections  or 
discs  (fig.  1 6)  is  developed  a  circle  of  tentacles  similar  to 
those  at  the  top  of  the  scyphostoma  when  it  began  to  di- 
vide. Below  this  circle  of  secondary  feelers  is  the  rem- 
nant of  the  old  scyphostoma.  The  strobila  stage  succeed- 
ing the  scyphostoma  is  now  completed.  The  uppermost 
and  oldest  disc  which  has  become  eight  lobed,  separates 
first,  then  the  others  follow  in  succession,  fig.  17  rep- 
resenting the  last  disc  about  to  drop  off.  This  free  stage 
of  the  Discophoran  is  known  as  the  ephyra.  After  sepa- 
ration the  ephyra  turns  over  (fig.  18,  enlarged  ten  diame- 
ters, with  the  lips  of  the  mouth  prominent)  and  is  a  well 
developed  medusa  (fig.  19,  natural  size).  The  parts  are 
better  seen  in  the  larger  species,  A.  aurita  Linn.  (Nos.  135, 
136).  The  most  important  organ  of  the  adult  is  the 
umbrella ;  this  is  usually  divided  into  eight  lobes  (No. 
136).  Hanging  from  the  center  of  the  lower  side  are  four 
long  oral  appendages.  A  system  of  tubes  extends  from 
the  central  digestive  cavity  to  the  circumference,  and  alter- 
nates with  another  system  which  connects  with  the  large 
genital  organs  on  the  dorsal  side  of  the  Aurelia. 


108  SYNOPTIC    COLLECTION. 

Aurelia  generally  develops  with  alternation  of  genera- 
tions, as  above  described,  but  in  isolated  cases  the  devel- 
opment is  accelerated,  the  hydroid  stage  being  omitted, 
and  the  medusa  develops  at  once  from  the  egg. 

In  Pelagia  noctiluca  Pe'r.  &  Less.  (No.  137),  the  sessile 
hydra  stage  is  always  omitted  and  the  parenchymella  de- 
velops without  intermediate  forms  into  the  medusa.  This 
process  is  not  comparable  with  the  simple,  primitive  de- 
velopment of  ancestral  forms,  nor  with  the  direct  develop- 
ment of  Aeginopsis;  neither  can  it  be  compared  with  the 
indirect  development  peculiar  to  those  forms  which  pass 
through  an  alternation  of  generations,  nor  with  the  sup- 
pressed development  observed  in  Hydra.  It  is  rather  an 
illustration  of  accelerated  development  which  character- 
izes not  the  primitive  but  the  secondary  and  specialized 
members  of  a  group. 

A  more  complicated  condition  is  found  in  Rhizostnma 
pulmo  Linn.  (Nos.  138,  139)  in  which  the  margins  of  the 
lips  have  become  united  so  that  the  food  is  taken  in 
through  a  large  number  of  minute  openings  in  the  tenta- 
cles. 

Haliclystus  auricula  Clark  (No.  140),  is  our  common 
Lucernarian.  It  is  a  beautiful  green  medusa  about  an 
inch  in  diameter  and  is  fastened  temporarily  by  a 
sucker  on  the  smaller  end  of  its  bo^ly.  The  habit  of 
creeping  peculiar  to  the  adult  Haliclystus  has  become 
fixed  in  the  young,  so  that  the  latter  is  not  free-swimming 
but  crawls  over  eel  grass  from  an  early  age.  This  is  also 
true  of  the  young  of  Lucernaria,  which  is  not  provided 
with  cilia  but  creeps  over  surfaces.  The  adult  Lucernaria 
(No.  141)  is  divided  into  eight  lobes.  The  cavity  of  the 
oral  cone  communicates  with  a  central  chamber  whence 
four  wide  chambers  pass  into  the  lobes. 


METAZOA — COELENTERA.  109 


SlPHONOPHORA. 

There  is  a  good  reason  for  placing  the  Siphonophora  as 
the  most  specialized  group  of  the  Hydrozoa,  since  the  proc- 
ess of  budding  which  we  have  found  in  the  larval  Hydra 
is  carried  back  to  a  still  earlier  stage  and  exists  in  the 
embryo  itself.  This  precocious  germ  develops  into  a  com- 
plex colony  of  hydra-like  and  medusa-like  zoons. 

Velella  mutica  Bosc  (No.  142)  in  addition  to  a  float  has 
a  triangular  sail.  According  to  A.  Agassiz,  Velella  has 
much  in  common  with  the  Tubularians,  the  young  medusa 
resembling  in  a  marked  degree  the  medusae  of  that  group. 

In  the  adult  Velella  a  single  feeding  zoon  extends 
downward  from  the  lower  side  and  around  it  are  many 
small  appendages  in  the  form  of  delicate  threads  which 
bear  tiny  medusae  buds ;  these  separate  and  swim  away. 
The  float  above  is  surmounted  by  the  sail  (finely  seen  in 
the  alcoholic  specimen,  No.  142)  which,  according  to 
Agassiz,1  is  left  handed  ;  that  is,  the  sail  runs  northwest 
and  southeast,  the  longitudinal  axis  of  the  float  being 
placed  north  and  south.  In  2500  specimens  thrown  on 
the  beaches  at  the  Tortugas  the  position  of  the  sail  was 
the  same,  showing  that  this  character  has  become  so 
firmly  fixed  in  the  organization  that  it  is  not  subject  to 
variation. 

Porpita  linnaeana  Less.  (No.  143;  No.  144,  preserved 
specimen;  No.  145,  model  of  P.  umbrella  Esch.),  proba- 
bly possesses  a  sail  in  youth  which  is  lost  in  maturity. 
It  has  a  central  disc,  the  upper  side  of  which  is  corru- 
gated. The  internal  structure  is  somewhat  complex. 
Long  and  short  tentacles  extend  from  the  edge  of  the  disc 
(No.  145),  and  these  are  provided  with  knobs  which  can 
be  seen  flattened  in  the  preserved  specimen  (No.  144). 
Near  the  disc  and  at  the  base  of  the  tentacles  are  the 

1  Mem.  Mus.  Comp.  Zool.,  VIII,  1883. 


110  SYNOPTIC    COLLECTION. 

feeding  and  reproductive  zoons.  The  latter  give  rise  to 
medusae  buds  which  may  be  seen  in  different  stages  of 
development  in  the  living  animals  until  finally  they 
become  detached  and  swim  away. 

Physalia,  or  the  Portuguese  Man-of-war  (No.  146;  No. 
147,  P.  arethusa  Till.;  No.  148,  model  of  P.  pelagica 
Linn.),  has  a  beautiful  pear-shaped  float  surmounted  by  a 
crest  or  sail,  well  seen  in  No.  147.  According  to  the 
observations  of  Huxley  on  young  Physaliae  it  is  probable 
that  the  float  represents  the  primary  Hydra.  At  the 
broader  end  of  the  lower  side  of  the  float  are  different 
kinds  of  zoons;  these  perform  a  different  kind  of  work 
and  are  therefore  unlike  in  structure.  Prof.  Agassiz 
observed  that  the  largest  zoons  are  on  the  windward  side 
of  the  animal  and  are  provided  with  tentacles  which  vary 
in  length  from  20  to  50  feet. 

The  feeding  zoons  are  of  two  kinds,  and  besides  these 
there  are  medusa  buds  which  do  not  break  away  as  free 
medusae  but  are  modified  into  swimming  or  propelling 
bells. 

•  Agalma  rigidum  Hkl,  (No.  149),  is  a  complex  organ- 
ism. It  has  a  flexible  hollow  stem  which  is  divided  into 
two  parts  and  which  bears  all  the  appendages.  At  one 
end  the  stem  enlarges  to  form  the  air-bladder  or  float 
which  is  reduced  and  apparently  too  small  to  be  function- 
ally useful.  The  two  parts  of  the  stem  are  called  the 
nectostem  and  polypstem.  The  nectostem  carries  bodies 
which  resemble  medusae  but  which  are  without  a  mouth 
or  stomach.  If  originally  medusae,  they  have  become 
reduced  into  propelling  organs  or  swimming  bells.  The 
polypstem  has  covering  scales  probably  for  protecting  the 
bodies  beneath  them.  These  bodies  are  of  three  differ- 
ent kinds:  nutritive  zoons,  small  organs  called  tasters 
which,  according  to  Haeckel,1  have  a  sensory  function 
acting  as  organs  of  taste  or  sight,  and  sexual  bells  or 

1  Chall.  Rep.,  Zool.,  XXVIII,  part  77,  1888,  Siphonophora,  p.  16. 


METAZOA COELENTERA.  Ill 

zoons.  The  first  have  long  tentacles  and  supply  nourish- 
ing fluids  to  the  whole  colony,  pouring  them  into  the 
cavity  of  the  stem,  the  common  reservoir  from  which  the 
swimming  bells  and  other  zoons  draw.  The  sexual  bells 
are  male  and  female  and  each  female  bell  contains  one  egg. 

Apolemia  (No.  150)  is  another  float-bearing  Siphono- 
phore  in  which  the  polypstem  has  the  covering  scales 
arranged  in  clusters  with  the  tasters,  feeding  and  repro- 
ductive zoons. 

Abyla  pentagona  Esch.  (No.  151),  undergoes  an  addi- 
tional process  in  the  course  of  its  development.  Each 
segment  of  the  Siphonophore  becomes  detached  and  lives 
an  independent  life.  It  is  a  feeding  zoon  with  two  loco- 
motive bells  for  swimming,  in  which  are  the  reproductive 
organs.  In  this  changed  condition  some  of  the  parts  may 
become  greatly  altered  in  form. 


CTENOPHORA. 

The  Ctenophora  are  interesting  since  they  possess 
characters  in  common  with  the  Hydrozoa,  the  Worms, 
and  the  Echinoderms.  It  may  be  they  have  arisen  from 
the  Anthomedusan,  Ctenaria  ctenophora,  and,  if  so,  they 
are  the  most  differentiated  of  Medusae.  On  the  other 
hand,  they  have  certain  structures  peculiar  to  the  Turbel- 
larian  worms,  while  the  possession  of  a  digestive  and 
water  vascular  system  in  communication  with  each  other 
points  to  a  relationship  with  the  Echinoderms.1  Accord- 
ing to  Chun,2  the  development  of  the  egg  of  the  Cteno- 
phora is  similar  in  the  different  genera,  but  the  varia- 
tions appear  during  the  postembryonic  development. 

The  group  is  represented  in  the  Collection  by  Pleuro- 

1  A.  Agassiz,  Mem.  Amer.  Acad.  Arts  and  Sci.,  X,  no.  3,  1874,  p. 

379- 

2  Fauna  und  Flora  des  Golfes  von  Neapel,  I,  Leipzig,  1880. 


112  SYNOPTIC    COLLECTION. 

brachia  rhododactyla  Ag.  (No.  152),  Cestum  veneris  Less. 
(No.  153).  Idyia  roseola  Ag.  (No.  154),  and  Beroe ovata 
Esch.  (No.  155). 

Pleurobrachia  rhododactyla  Ag.  (No.  152),  is  frequently 
seen  off  the  New  England  coast.  Its  transparent  body  is 
spherical,  with  eight  rows  of  comb-like  structures  or  plates 
extending  from  pole  to  pole.  These  are,  in  reality,  cilia 
which  have  become  united,  as  shown  by  the  development 
of  the  animal.  They  constitute  the  peculiar  characteristic 
of  this  group,  giving  it  the  name  Ctenophora.  The  ex- 
tremely long  tentacles  may  extend  from  the  body  or  else 
be  tucked  away  out  of  sight  in  two  lateral  pockets.  It 
has  been  found  that  another  Ctenophoran,  Bolina,  is  so 
similar  to  Pleurobrachia  when  it  leaves  the  egg,  that  one 
cannot  be  distinguished  from  the  other  except  that  the 
compression  of  the  body  in  Bolina  is  in  a  plane  at  right 
angles  to  that  of  Pleurobrachia.  The  postern bryonic  de- 
velopment, however,  produces  marked  changes  of  form, 
complex  windings  of  .  vessels,  and  the  almost  complete 
disappearance  of  tentacles  which  are  at  first  developed 
like  those  of  Pleurobraehia. 

Cestum  veneris  Less.  (No.  153),  is  instructive  on  ac- 
count of  its  phylogenetic  relations  to  other  Ctenophora. 
There  are  few  groups  of  the  animal  kingdom  where  the 
postembryonic  metamorphosis  so  strikingly  recapitulates, 
even  in  the  details  of  organization,  the  adult  forms  of 
more  simply  organized  groups,  as  do  the  larval  stages  of 
Cestum  and  the  lobed  Ctenophora  recapitulate  the  adult 
stages  of  the  generalized  Ctenophora.1 

The  adult  Cestum  has  distinct  bilateral  symmetry.  Its 
long,  belt-like  appearance  has  won  for  it  the  name  of 
Venus's  girdle.  Eight  rows  of  plates  or  combs  extend 
longitudinally  down  the  body,  and  these  aid  in  locomotion. 
The  mouth  is  near  the  middle  of  the  belt-like  body  and 
possesses  two  tentacles  which  extend  from  a  pocket. 

1Allman,  On  the  Development  of  Ctenophora,  Journ.  Linn.  Soc. 
London,  Zool.,  XVI,  1882,  p.  106. 


METAZOA COELENTERA.  113 

Idyia  roseola  Ag.  (No.  154)  and  Beroe ' ovata  Esch.  (No. 
155)  are  elongated  in  form  and  both  are  without  tentacles. 


Sections  3,  4. —  ANTHOZOA. 

ALCYONARIA. 

It  is  reasonable  to  suppose  from  what  is  already  known 
that  the  ancestral  form  of  the  Anthozoa  possessed  a  simple, 
tubular,  fleshy  body  with  a  mouth  at  the  end  of  an  oral 
cone,  at  the  base  of  which  was  a  limited  number  of  solid 
tentacles.  Such  a  form  would  resemble  closely  the  scy- 
phostoma  of  the  Hydrozoa,  and  the  majority  of  naturalists 
consider  this  as  the  ancestral  form  of  the  Anthozoa.  If  we 
imagine  the  oral  cone  of  the  scyphostoma  turned  inward, 
we  have  an  internal  bag  hanging  within  the  body  cavity. 
Again,-  if  we  suppose  that  the  fleshy  walls  or  mesenteries 
which  are  indicated  in  Cyanea  (see  p.  107)  grow  longer 
and  join  the  central  bag,  then  we  have  the  hydroid  plan 
of  structure  converted  into  the  Actinian  plan.  This  is 
a  crude  but  graphic  way  of  illustrating  the  hydroid  and 
the  Actinian  type  of  structure  and  the  possible  conversion 
of  the  one  into  the  other,  although  it  must  be  remembered 
that  there  are  no  embryological  facts  to  prove  that  these 
changes  actually  took  place.1 

This  early  ancestral  form  probably  followed  essentially 
the  same  path  of  development  as  the  hydroid,  since  the 
Actinian  of  to-day  passes  through  the  blastula,  parenchy- 
mella,  and  secondary  gastrula  (not  invaginated)  stages. 
While,  however,  the  parenchymellaof  the  hydroid  is  usually 
produced  by  the  immigration  of  cells  from  the  surface  to 
the  interior,  that  of  the  Anthozoa  is  generally  made  by 
delamination  of  the  inner  ends  of  the  ectoderm  cells. 
This  process  is  brought  about  through  differentiation  of 

IE.  B.  Wilson,  Phil.  Trans.,  CLXXIV,  1883,  p.  762. 


114  SYNOPTIC    COLLECTION. 

these  parts  of   the  cells,  owing    to  the  accumulation  in 
them  of  food  material. 

It  is  probable  from  the  evidence  now  at  hand  that  the 
ancestral  form  above  described,  developed  four  mesen- 
teries. The  Hexactiniae,  to  be  described  farther  on,  pass 
through  a  stage  with  four  mesenteries,  which  antedates 
the  Edwardsia  stage  of  eight  mesenteries.  This  form 
may  have  given  rise  to  a  branch  which  through  continued 
specialization  reached  the  condition  now  shown  in  the 
Alcyonaria.  It  is  customary  to  consider  the  Alcyonaria 
as  more  specialized  than  the  Hexactiniae,  and  for  this 
reason  they  are  generally  placed  after  this  group;  but  set 
ting  aside  their  variety  of  form  and  delicacy  of  structure, 
they  seem  in  reality  more  simple,  especially  when  the 
single,  generalized  Alcyonarians  are  considered. 

There  is  also  another  good  reason  for  placing  the  Alcyo- 
naria as  the  more  primitive  group.  Recent  investiga- 
tions1 upon  Alcyonaria  and  the  ancient  tabulate  corals 
tend  to  prove  that  the  latter  group  (with  the  exception  of 
a  few  species)  are  ancestral  forms  of  the  Alcyonaria. 
For  this  reason  some  of  the  tabulate  corals  have  been 
taken  from  the  Zoantharia  where  hitherto  they  have  been 
placed,  and  are  here  considered  as  the  primitive  fore- 
runners of  the  Alcyonaria. 

Cladochonus  (  =  Pyrgia)  michelini  M.-Ed.  &  H.,  is  a 
single,  trumpet-shaped  form  when  young  (PI.  156,  fig.  i, 
natural  size;  fig.  2,  enlarged),  and  though  without  pores, 
walls,  or  horizontal  floors,  called  tabulae,  it  is  probably 
related  to  Aulopora  (No.  157)  and  the  other  tabulate 
corals.  When  mature  it  forms  a  simple  colony  and  the 
zoons  are  attached  by  processes  which  extend  from  the 
lower  surface.  These  are  seen  in  PI.  156,  figs,  i,  2. 


1  Sardeson,  Ueber  die  Beziehungen  der  fossilen  Tabulaten  zu  den 
Alcyonarien.  Neues  Jahrb.  f.  Min.,  Geol.  u.  Pal.,  Beilage  Band  X, 
Heft  3,  1896;  see  also  Moseley,  Chall.  Rep.,  Zool.,  II,  part  7,  1881, 
p.  102. 


METAZOA COELENTERA.  115 

AuJopora  serpens  Goldf.  (No.  157)  begins  as  a  single  form, 
then  by  budding,  a  creeping,  irregular  colony  is  produced. 
The  origin  and  structure  of  a  compound  coral  is  illustrated 
by  Pleurodictyum  lenticulare  Hall  (PL  158,  figs.  1-9). 
The  first  coral  animal  that  started  the  colony  was  single. 
Its  skeleton  was  shaped  like  an  inverted  cone  smooth  in 
the  earliest  and  ribbed  in  the  later  stage  (figs.  1,2,  3). 
At  first  the  interior  is  simply  granulose.  but  above  the 
middle  portion  the  granules  are  arranged  in  rows  which 
are  probably  the  beginnings  of  walls.  When  limy  walls 
exist  in  the  Alcyonaria,  they  riiay  be  called  pseudosepta, 
since  the  true  septa  of  the  Hexactiniae  correspond  in 
disposition  and  number  to  the  fleshy  mesenteries,  which 
cannot  be  said  of  the  walls  of  the  Alcyonaria  in  general. 
These  rudimentary  walls  are  without  pores  and  the  whole 
skeleton  is  covered  by  an  external  limy  layer,  the  epitheca. 

Thus  it  is  seen  that  the  primitive  ancestral  form  of  corals, 
as  proved  by  this  first  stage  of  the  compound  coral,  is 
extremely  simple,  imperforate,  and  without  tabulae  or 
well  developed  walls.  In  the  next  stage  a  bud  appears 
which  is  in  direct  communication  with  the  parent  form, 
giving  rise  to  an  opening  or  pore  in  the  wall  of  the  latter 
(fig.  4).  This  is  the  Aulopora  stage  which  is  seen  more 
clearly  in  fig.  5.  Some  doubt  exists  in  regard  to  this 
figure,  but  in  all  respects  excepting  the  position  and  direc- 
tion of  the  bud,  this  form  agrees  with  Pleurodictyum  lenti- 
culare and  may  therefore  be  regarded  as  one  of  its  early 
stages.  The  buds  appear  alternately  (figs.  6,  7,  8)  until 
a  circle  surrounds  the  original  form  (fig.  9).  The  second 
stage  is  now  completed.  The  colony  increases  twice  in 
diameter  until  the  mature  condition  is  reached. 

The  origin  and  growth  of  the  colony  of  Michelinia  con- 
vexa  d'Orb.,  are  shown  diagrammatically  in  PL  159,  figs. 
1-7.  In  fig.  i  the  first  corallite  is  represented  in  the  cen- 
ter with  its  circle  of  corallites  which  have  arisen  alter- 
nately, as  in  Pleurodictyum  lenticulare.  Michelinia,  how- 
ever, advances  farther  than  the  last  named  coral  and 


116  SYNOPTIC    COLLECTION. 

builds  up  a  large  colony  by  a  process  of  intermural  bud- 
ding. Fig.  2  shows  how  the  buds  are  given  off  between 
the  walls  of  the  coral Utes,  truncating  three  angles  of  the 
parent  form.  Next,  three  more  buds  appear,  truncating 
the  other  three  angles  and  pushing  the  original  circle  far- 
ther away  (fig.  3).  Fig.  4  shows  the  circle  of  intermural 
buds  larger  in  size,  while  the  buds  between  the  walls  of 
the  original  circle  (three  of  which  are  seen  in  fig.  3) 
have  been  formed.  These  have  increased  in  size  in  fig.  5. 
In  fig.  6  all  these  buds  have  grown  and  the  corallites  of  the 
original  circle  are  separated  not  only  from  the  parent  form 
but  also  from  one  another.  Fig.  7  gives  a  vertical  view  of 
the  same,  the  numbers  1-6  corresponding  with  the  numbers 
of  the  views  seen  from  above.  These  figures  illustrate 
finely  how  the  shape  of  the  corallites  is  due  to  pressure. 

Favosites  (No.  160)  is  a  compound  colony  like  Miche- 
linia.  Its  development  follows  the  same  general  law  that 
governs  the  intermural  budding  of  Michelinia,  but  is 
more  complicated,  owing  probably  to  acceleration  in  de- 
velopment. Girty1  has  shown  that  the  colony  springs 
from  a  single  animal  which  is  similar  in  general  aspect  to 
the  original  zoon  of  Pleurodictyum.  This  zoon  is  pros- 
trate, slightly  curved  at  first,  and  is  attached  by  its  dorsal 
side.  When  full  grown  the  zoon  is  more  erect  and  gives 
off  four  buds  from  its  dorsal  side.  Each  is  connected 
with  the  parent  form  by  means  of  a  pore.  Next,  five  buds 
appear  in  the  peripheral  spaces  between  those  already 
existing.  It  is  not  until  there  are  nineteen  buds  that  the 
original  one  is  surrounded.  In  this  one-sided  or  unilateral 
budding  Favosites  differs  from  the  last  two  colonies  de- 
scribed. 

The  generalized  members  of  the  living  Alcyonaria — 
the  Proto- Alcyonaria  —  are  the  three  genera  Monoxenia, 
Hartea,  and  Haimea;  of  these,  Monoxenia  is  represented 
in  the  Collection  by  a  drawing.  It  is  unfortunate  that 

1  Amer.  Geol.,  XV,  Mar.,  1895. 


METAZOA COELENTERA.  117 

scarcely  anything  is  known  of  the  development  of  these 
primitive  forms,  since  this  knowledge  would  doubtless 
throw  light  on  the  phylogeny  of  the  Anthozoa. 
,  Monoxenia  (PI.  161,  greatly  enlarged)  never  secretes 
a  skeleton  or  any  hard  parts.  Its  tubular  fleshy  body  has 
only  eight  tentacles  (PI.  161)  and  these  are  hollow  pro- 
longations of  the  internal  cavity  (PI.  162,  fig.  i,  longi- 
tudinal section  of  the  body) .  The  internal  structure  is 
simple,  since  there  are  only  eight  mesenteries  (PI.  162, 
fig.  2).  These  bear  clusters  of  eggs  which  are  also  seen 
in  fig.  i.  The  cross  section  is  made  near  the  central  part 
of  the  body  cavity  which  is  marked  by  the  dotted  line. 
It  cuts  through  a  mesentery  on  one  side  and  between  two 
mesenteries  on  the  other. 

Hartea  is  another  simple  form  with  eight  tentacles  and 
mesenteries,  but  in  this  case  the  base  of  the  body  and 
the  tentacles  are  provided  with  star-shaped  spicules. 
Haimea  has  variously  shaped  spicules  and  this  gen  us  also 
possesses  thread  cells  or  nematocysts. 

In  these  three  genera  no  ciliated  groove  (siphono- 
glyph)  at  one  end  of  the  mouth  opening  has  been 
described,  and  probably  none  exists.  The  last  two  gen- 
era have  a  skeleton  consisting  of  spicules.  They  are 
found  only  on  the  base  or  in  the  body  walls  and  are 
never  secreted  in  the  body  cavily ;  there  are  therefore  no 
false  nor  true  septa.  This  can  be  said  not  only  of  these 
genera  but  also  of  all  living  Alcyonaria,  and  it  is  prob- 
able that  this  changed  and  reduced  condition  of  the 
skeleton  has  been  brought  about  since  the  tabulate 
ancestors  of  the  Alcyonaria  flourished  in  Palaeozoic 
times. 

From  single  forms  we  pass  to  simple  colonies.  Cornu- 
laria  cornucopiae  Lam.,  is  a  simple  colony  without  spic- 
ules but  with  more  or  less  horny  matter.  It  is  interesting 
to  note  that  in  this  species  the  ectoderm  secretes  a  horny 
sheath  (PI.  163,  fig.  i)  which  reminds  one  of  the  external 
skeleton  of  the  hydroids. 


118  SYNOPTIC    COLLECTION. 

A  related  genus,  Clavularia  crassa  M.  &  K.  (PI.  163, 
fig.  2),  is  a  simple  colony  with  retractile  zoons.  It  has 
spicules  but  no  horny  sheath.  In  Clavularia  viridis  Q. 
&  G.,  the  first  zoons  spring  from  the  basal  stolon,  but 
higher  up  they  are  united  by  simple  tubes  from  which 
other  zoons  are  budded  (see  PI.  164,  fig.  i,  showing  the 
skeleton  of  a  zoon  that  has  budded  from  the  connecting 
tube).  The  grooves  on  the  surface  of  the  skeleton  mark 
the  position  of  the  eight  mesenteries  within.  The  skel- 
eton consists  of  a  coriaceous  substance  with  a  few 
scattered  spicules,  and  is  without  openings,  therefore 
imperforate. 

Clavularia  glauca  Hickson1  (  =  Anthelia  glauca  Savig.) 
(No.  165)  puts  out  a  fleshy  membrane,  the  coenosarc,  from 
the  bases  of  the  zoons ;  this  fleshy  floor  is  provided  with 
nutritive  canals  and  secretes  the  limy  coenenchyma. 

The  organ-pipe  coral,  Tubipora  hemprichi  Ehr.  (No. 
1 66),  when  young  has  a  long,  tubular,  fleshy  body  with 
the  mouth  in  the  middle  of  the  oral  disc  surrounded  by 
eight  tentacles.  The  latter  are  fringed  with  small  papil- 
lae, each  one  of  which  has  a  tiny  opening  at  the  end. 
The  basal  portion  of  the  body  sends  out  a  fleshy  layer 
which  extends  over  the  surface  of  the  rock  and  from 
which  other  zoons  are  budded.  As  the  colony  increases 
in  size  this  flat  lamella  ceases  to  grow  and  its  work  of 
giving  origin  to  new  zoons  is  at  an  end.  Around  the  oral 
end  of  the  body  there  spreads  out  a  rim  (No.  166).  This 
may  surround  neighboring  tubes  or  fuse  with  adjacent 
rims,  thereby  forming  horizontal  platforms  from  which 
other  zoons  arise. 

The  spicules  first  appear  singly  in  the  mesoderm  of  the 
base  and  walls  of  the  tubes  and  of  the  cross  platforms, 
but  during  the  growth  of  the  animals  they  become  united 
by  the  serrations  of  their  edges  to  form  a  solid  skeleton 
(N"o.  167).  The  sutures  between  the  spicules  can  be 

1  See  Trans.  Zool.  Soc.  London,  XIII,  1892,  p.  333. 


METAZOA COELENTERA.  119 

plainly  seen  with  the  microscope ;  they  extend  crosswise, 
as  do  also  the  long  axes  of  the  spicules.  Occasionally, 
according  to  Hickson,  they  project  into  the  cavity  of  the 
coral  animal  and  look  like  the  so  called  "  septa "  of 
Syringopora.  No  true  septa  are  developed  in  Tubipora 
but  within  the  tubes  are  found  variously  shaped  tabulae, 
some  flat  and  others  funnel-shaped.  It  is  an  interesting 
fact  that  at  the  free  end  of  the  zoon  the  spicules  are  sep- 
arate as  they  were  in  the  single  form  that  started  the 
colony. 

The  danger  of  multiplying  species  that  really  do  not 
exist  in  nature  has  recently  been  pointed  out  by  Hickson,1 
who  states  that  the  principal  character  which  has  been 
used  for  distinguishing  species  of  Tubipora  is  the  diameter 
of  the  zoQn  walls,  "and  this  character  in  every  specimen 
depends  entirely  upon  the  situation  on  the  reef  in  which 
it  happened  to  grow."  "Our  desire  to  make  new  species," 
says  this  author  elsewhere,  "seems  to  have  blinded  us  to 
what  is  perhaps  the  most  important  feature  of  Zoophytes 
—  the  infinite  variety  of  growth  they  may  exhibit  to  meet 
the  varying  conditions  of  their  existence."2 

Parakyonium  elegans  M.-Ed.  &  H.,  (No.  168)  is  a  colo- 
nial form  with  a  spicular  skeleton.  The  lower,  stem-like 
portion  is  more  dense  than  the  upper  part. and  is  without 
zoons,  while  the  small  branches  which  are  given  off  from 
the  upper  portion  are  covered  with  zoons.  Most  of  this 
part  can  be  withdrawn  to  the  stem.  The  zoons  have  very 
long  tubes  which  can  be  seen  in  a  vertical  section  extend- 
ing from  the  stem  to  the  surface.  Surrounding  these  is  a 
thick  coenenchyma  which  reaches  up  to  the  retractile  por- 
tion. The  body  cavities  communicate  with  one  another 
by  a  system  of  nutritive  canals.  Alcyonium  palmatum 
Pallas  (No.  169,  the  remaining  Alcyonaria  are  placed,  on 


1  A.  Willey,  Zoological  Results,  part  4,  Apr.,  1900,  p.  493. 
8  Trans,  and  Ann.  Rep.  Manchester  Micr.  Soc.,  Address  of  Presi- 
dent, 1899. 


120  SYNOPTIC    COLLECTION. 

account  of  their  shape,  in  the  erect  portion  of  Section  3) 
resembles  Paralcyonium.  The  colony  is  supported  by 
a  short  stem  which  is  often  without  zoons  and  broad- 
ens out  into  several  lobed  masses  which  are  thickly 
covered  with  coral  animals.  This  genus  is  sometimes 
imbedded  in  sand  while  other  species  attach  themselves 
to  the  stems  of  plants. 

Ammothea  nitida  Verr.  (No.  170),  may  have  finger-like 
projections  extending  from  a  flat  base.  The  zoons  in 
this  case  are  not  retractile. 

Spongodes  celosia^Less.  (No.  171),  is  a  colonial  form  in 
which  the  cortex  of  the  stem  and  branches  contains  large 
spicules.  The  zoons  are  not  retractile  and  their  tops  are 
protected  by  spindle-shaped  spicules. 

Virgularia  (No.  172)  bears  the  zoons  nearly.sessile  on 
the  central  stem.  This  genus  with  the  one  that  follows,  is 
among  the  simpler  forms  of  the  Pennatulidae  and  they 
are  both  found  in  deep  water.  Kophobelemnon  (No. 
173,^.  stelliferum  O.  F.  Mull.)  has  the  central  stem 
thick  and  bears  large  retractile  zoons. 

The  more  complex  Pennatulidae  are  represented  by  Pen- 
natula  aculeata  Dan.  &  Rev.  (No.  174),  Pennatula phospho- 
rea  Linn.  (No.  175),  and  Pennatula  rubra  Ellis  (No.  176). 
In  this  genus  there  is  a  long  central  stem  with  well 
developed  zoons  on  more  than  a  half  of  its  length.  The 
stem  is  deeply  grooved  on  the  dorsal  side  and  the  lower 
portion  is  sunk  in  sand  and  mud.  These  zoons  are 
dimorphic,  some  being  sexual  and  others  without  repro- 
ductive organs. 

In  Renilla,  (PI.  177  ;  Nos.  178,  179),  the  sexes  are  dis- 
tinct and  the  eggs  and  spermatozoa  are  discharged  at  the 
same  time,  fertilization  taking  place  in  the  water.  It  is 
interesting  to  note  that  the  segmentation  of  the  egg  is  so 
extremely  variable  "it  is  safe  to  say  no  two  eggs  ever 
develop  in  precisely  the  same  way." 

The  following  life  history  illustrates  the  good  results 
which  may  be  obtained  when  naturalists  cooperate  for  a 


METAZOA —  COELENTERA.  121 

common  object.  Three  investigators1  worked  together 
on  the  eggs  of  Renilla,  keeping  them  under  continuous 
observation,  and  "were  thus  enabled  to  determine  with 
all  possible  certainty  the  fact  that  at  least  five  or  six  well- 
marked  modes  of  yolk  cleavage  with  many  minor  varia- 
tions, may  occur  as  normal  phenomena  of  development, 
that  the  segmentation  may  be  at  first  equal  or  unequal, 
complete  or  partial,  regular  or  irregular,  and  that  a  great 
amount  of  variation  exists  in  the  duration  of  the  various 
stages  of  activity  and  quiescence." 

PL  177,  figs.  1-14,  illustrates  the  consecutive  stages  of 
development  in  one  individual,  the  time  required  being 
115  minutes.  The  egg  first  divided  into  eight  spheres 
(one  third  of  the  specimens  examined  divided  in  this  way, 
but  usually  this  stage  is  skipped  and  the  egg  cleaves  at 
once  into  sixteen  spheres).  When  the  sixteen-sphere 
stage  is  reached  the  process  of  delamination  begins. 
This  process  does  not  go  on  simultaneously  in  all  the 
spheres  but  occurs  later  in  some  cells  than  in  others. 
Fig.  15  is  a  section  of  the  embryo  in  which  the  inner  ends 
of  the  cells  are  separating  or  have  just  separated  from 
the  outer  portion.  The  cavities  seen  in  the  figure  are 
caused  by  shrinkage.  Fig.  16  shows  the  process  of 
delamination  completed.  At  this  time  the  egg  consists 
of  a  solid  mass  of  cells  in  which  there  is  no  trace  of  the 
segmentation  cavity.  The  cells  of  the  outside  and  of  the 
central  mass  grow  smaller  in  size  as  they  increase  in 
number.  Fig.  17  gives  in  outline  the  shape  of  a  larva 
twelve  hours  old.  When  the  embryo  is  about  twenty 
hours  old  a  change  begins  to  take  place,  and  a  few  hours 
later  the  endoderm  appears  by  a  differentiation  of  those 
cells  of  the  central  mass  lying  just  under  the  outer  layer. 
This  is  well  seen  in  figs.  18  and  19. 

Fig.  20  is  a  twenty-four  hours  old  embryo.  It  is  now 
covered  with  cilia  which  at  first  do  not  possess  the  power 

1  See  E.  B.  Wilson,  Phil.  Trans.,  London,  1883,  p.  723. 


122  SYNOPTIC   COLLECTION. 

of  motion,  but  afterwards  become  active,  propelling  the 
larva  through  the  water.  When  the  larva  is  twenty- 
eight  hours  old  the  ends  of  the  ectoderm  cells  are  swollen 
and  bulbous,  as  seen  in  fig.  21,  and  the  ball-like  portion 
separates  off  to  form  the  supporting  lamella  or  mesoderm 
(fig.  22,  m).  At  the  end  of  forty-eight  hours  all  the 
central  cells  not  used  in  the  formation  of  the  endoderm 
have  been  absorbed  as  food  by  the  endoderm  cells  and 
the  central  region  is  an  empty  cavity.  In  this  case,  as 
pointed  out  by  Wilson,  digestion  in  the  young  Renilla  is 
intra-cellular  or  amoeboid.  This  is  the  most  primitive 
mode  of  digestion  and  is  probably  inherited  by  the  Pori- 
fera  and  Coelentera  from  the  Protozoa. 

Usually  between  the  fortieth  and  fiftieth  hour  the 
internal  bag  is  formed  and  the  central  cavity  is  divided 
into  chambers  by  mesenteries.  The  cells  at  the  large 
end  of  the  body  increase  rapidly  and  are  pushed  inward 
in  a  solid  mass  (fig.  23,^),  forming  a  plug.  In  time  a 
narrow  cavity  is  seen  in  its  center  (fig.  24,  c),  This 
cavity  has  no  communication  with  the  exterior  for  twenty 
to  twenty-five  hours.  At  the  end  of  this  time  the  cavity 
breaks  through  and  a  mouth  is  formed ;  afterward  an 
opening  occurs  at  the  lower  end,  placing  the  internal  bag 
in  communication  with  the  central  cavity.  As  already 
stated,  the  mesenteries  appear  at  the  same  time  that  the 
bag  is  formed.  They  consist  of  eight  thick  plates-  of 
endoderm  cells  which  extend  down  from  the  oral  end  of 
the  body  and  are  of  different  lengths.  These  are  seen 
in  fig.  25,  which  is  a  cross  section  of  the  anterior  part  of 
a  forty-eight  hours'  larva,  and  in  fig.  26,  a  cross  section 
of  the  posterior  portion  of  a  four  days'  larva.  In  the 
living  animal  thes.e  mesenteries  arise  as  bilateral  organs ; 
that  is,  they  appear  one  on  either  side  of  the  median 
plane  of  the  body.  (The  figures  25  and  26  should  be 
turned  slightly  to  show  the  bilateral  condition  more 
plainly.  The  dotted  line  in  fig.  26  indicates  the  median 
plane  of  the  body.)  For  the  reason  that  these  partitions 


METAZOA — COELENTERA.  123 

are  single  and  are  arranged  four  on  each  side  of  the 
median  line  of  the  body  they  are  called  bilateral  mesen- 
teries. They  can  be  distinguished  from  the  biradial 
mesenteries  of  the  Hexactiniae  s:nce  these  arise  in  pairs 
that  radiate  from  the  center  to  the  circumference.  When 
the  animal  is  placed  in  accordance  with  this  bilateral 
arrangement,  there  is  a  dorsal  and  a  ventral  side.  The 
former  differs  from  the  latter  by  having  the  mesenteries 
much  shorter,  as  shown  in  fig.  26.  These  walls  may  be 
seen  on  the  outside  in  a  three-and-a-half  days'  larva  (fig. 
27  ;  fig.  28,  the  same  contracted). 

It  is  at  this  early  time  or  even  a  little  earlier  (seventy- 
two  hours)  that  buds  appear,  as  will  be  described  farther 
on. 

Figures  29  and  30  show  the  larva  when  it  has  settled. 
The  tentacles  are  at  first  quite  simple  but  during  growth 
become  pinnate.  The  fact  that,  according  to  Wilson,  the 
eight  mesenteries  and  eight  tentacles  appear  at  one  time 
and  not  in  sequence,  as  is  the  case  in  the  Hexactiniae, 
does  not  prove  that  the  Alcyonaria  are  more  specialized 
than  the  Hexactiniae.  In  order  to  demonstrate  this 
view,  evidences  of  the  reduced  character  of  the  Hexac- 
tiniae, such  as  the  reduction  of  biradial  mesenteries, 
must  be  brought  forward.  The  abbreviated  record  in 
the  development  of  forms  like  Renilla  tends  to  prove  that 
these  are  more  specialized  members  of  the  Alcyonaria, 
and  we  should  predict  that  the  primitive  forms  of  the 
group  would  show  a  regular  sequence  in  the  appearance 
of  the  mesenteries. 

The  spicules  of  Renilla  are  formed,  according  to 
Wilson,  in  both  the  endoderm  and  the  ectoderm.  Those 
of  the  endoderm  appear  first ;  they  are  oval  nodules  and 
are  not  numerous.  Fig.  31  represents  a  young  stage;  fig. 
32,  an  old  stage  ;  and  fig.  33,  the  spicule  taken  from  the 
cell.  The  spicules  of  the  ectoderm  appear  soon  after 
the  attachment  of  the  larva.  They  are  at  first  rod-like 
and  colorless,  and  not  until  a  colony  is  formed,  do  they 


124  SYNOPTIC    COLLECTION. 

become  purple.  Figs.  34  and  35  are  ectoderm  cells  con- 
taining young  spicules  ^  fig.  34  being  not  more  than  one 
eighth  the  length  of  a  fully  formed  spicule.  The  calcare- 
ous matter  first  takes  the  form  of  elongated  concretions 
and  these  like  the  endodermic  spicules  are  formed  by  a 
process  of  crystallization,  as  shown  by  Prof.  B.  K. 
Emerson.  It  is  an  interesting  fact  that  the  development 
of  the  spicules  in  the  Alcyonaria  is  similar  to  the  forma- 
tion of  these  hard  parts  in  the  mesoderm  of  sponges,  as 
observed  by  Schultze  and  Metschnikoff,  and  seems  not 
unlike  the  formation  of  crystals  in  vegetable  cells,  as  sug- 
gested by  Wilson. 

It  has  already  been  stated  that  the  larva  begins  to  form 
a  colony  while  it  is  free.  It  is  probable,  as  pointed  out 
by  Wilson,  that  the  necessity  for  motion  is  the  cause  for 
the  early  development  of  the  buds.  If  the  parent  after 
becoming  attached  had  no  means  of  moving,  it  would 
doubtless  be  "smothered  in  the  drifting  sand."  The 
position  of  the  first  two  buds,  as  seen  in  fig.  27,  is  con- 
stant. The  development  differs  from  that  of  the  parent 
zoon  which  has  arisen  from  an  egg,  so  that  one  ought  not 
to  compare  egg  development  with  bud  development. 
The  young  colony  takes  in  water  and  by  means  of  strong 
internal  currents  is  able  to  creep. 

It  is  instructive  to  note  that  an  allied  genus,  Leptogor- 
gia,  does  not  possess  the  power  of  creeping  but  fastens 
itself  early  in  life  to  safe  objects,  and  Dr.  Wilson  detected 
no  buds  at  the  end  of  two  months.  Fig.  36  is  a  young 
colony  with  five  pairs  of  buds.  In  the  adult  (No.  178, 
with  zoon  expanded;  No.  179,  contracted)  the  young 
marginal  zoons  move  the  whole  colony,  and  as  they 
mature,  become  nutritive  and  reproductive.  In  time  the 
zoons  of  this  primary  group  become  centers  of  multiplica- 
tion and  many  secondary  groups  are  formed,  while  com- 
plexity marks  the  whole  organization. 

The  marked  bilateral  symmetry  of  Renilla  is  an  evi- 
dence that  the  group  to  which  it  belongs  is  more  primitive 


METAZOA COELENTERA.  125 

than  the  Hexactiniae,  since  the  latter  are  bilateral  in  early 
life  and  become  radiate  afterward,  owing  to  attachment 
and  the  action  of  physical  forces. 

Another  colonial  form  is  Veretillum  (No.  180)  which 
is  related  to  Renilla. 

Briareum  (No.  181,  see  upper  shelf)  of  the  Gorgon- 
acea  is  an  upright,  irregularly  lobed  colony.  The 
zoons  are  without  protecting  cups  and  can  be  entirely 
withdrawn  into  the  coenenchyma  which  is  abundantly 
supplied  with  spicules.  The  central  mass,  which  can 
hardly  be  called  an  axis,  is  supplied  with  nutritive  canals. 

In  Melitodes,  (No.  182,  M.  ochracea  Verr.),  the  axis  is 
jointed  and  the  sections  consist  of  alternating  portions  of 
horny  and  calcareous  matter.  The  horny  sections  are  in 
reality  made  of  a  horny  substance  and  loose  spicules, 
while  the  calcareous  parts  are  composed  of  consolidated 
spicules.  All  the  joints  are  penetrated  by  canals. 

The  spicules  in  Corallium  rubrum  Linn.  (No.  183), 
unite  to  form  a  dense  calcareous  axis  (No.  184),  which 
is  a  beautiful  red  color  and  used  for  ornaments.  The 
young  coral  animal  has  a  mouth  surrounded  by  eight 
white,  pinnate  tentacles  (No.  183).  The  internal  bag 
leads  into  the  body  cavity  which  is  divided  by  eight 
mesenteries  into  eight  chambers.  The  outer  flesh  is  a 
bright  red  color  and  is  stiffened  by  spicules.  This  single 
zoon  buds  and  a  colony  arises.  The  body  cavities  of  all 
the  zoons  connect  with  a  series  of  water  tubes  ;  these 
press  upon  the  calcareous  stem  which  is  secreted  by  the 
bases  of  the  zoons  and  while  it  is  yet  soft,  indent  its 
surface. 

Isis  (No.  185)  has  a  jointed  axis  consisting  of  horny 
and  silicious  sections.  The  zoons  can  be  withdrawn  into 
the  thick  coenenchyma.  The  spicules  are  club-shaped 
and  stellate  in  form. 

An  upright  colony  is  formed  by  Xiphigorgia  (No.  186). 
A  related  form,  Plexaura  (No.  187),  has  a  horny  axis, 
while  the  coenenchyma  has  variously  shaped  spicules. 


126  SYNOPTIC    COLLECTION. 

Small  canals  radiate  from  the  cavities  of  the  zoons  and 
open  into  the  longitudinal  canals  around  the  axis. 

The  fan  coral,  Rhipidogorgia.  (No.  188)  is  another 
upright  coral,  the  branches  of  which  unite  to  form  a  net- 
work. The  zoons  are  arranged  on  either  side  of  the 
intersecting  branches.  The  yellow  flesh  is  stiffened  by 
spicules  of  different  shapes  and  the  axis  (No.  189)  is 
horny. 

ANTHOZOA. 
ZOANTHARIA. 

Coming  to  the  present  day  we  find  among  living 
Zoantharia  the  fleshy  Actiniae  which  never  make  a  skele- 
ton. The  researches  of  Boveri,1  McMurrich,2  and  others 
make  it  very  probable  that  all  the  Actinian  types  have 
descended  directly  or  indirectly  from  the  Edwardsiae. 

Edwardsiae.  Edwardsia  claparedi  Pane.  (PI.  190, 
figs,  i,  2)  is  a  single  form  with  eight  simple  tentacles. 
Its  body  cavity  is  divided  into  chambers  by  eight  bilateral 
mesenteries  (fig.  2).  These  Actiniae  have  the  dorsal 
and  ventral  differentiation  of  the  body  well  marked,  so 
that  a  bilateral  arrangement  of  the  parts  is  the  predomi- 
nating characteristic  (fig.  2).  When  young,  Edwardsia 
is  free-swimming,  but  later  it  becomes  stationary  by 
burying  the  posterior  part  of  its  body  in  sand.  A  related 
form,  Cerianthus  membranaceus  (No.  191)  has  a  similar 
habit. 

Antipathes  subpinnata  (No.  192)  represents  the  Anti- 
pathariae.  -Nothing  has  been  done  as  yet  with  the  embryo- 
logical  development  of  this  group.  The  young  Antipathes 
is  a  single,  fleshy  animal.  At  one  end  is  the  mouth  with 

'Zeitschr.  f.  wiss.  Zool.,  XLIX,  1889,  p.  492. 

2Journ.  of  Morph.,  IV,  V,  1 890^9 1  ;  Proc.  U.  S.  Nat.  Mus., 
XVI,  1893. 


METAZOA COELENTERA.  1 27 

six  simple  tentacles.  The  mouth  leads  into  an  internal 
bag l  which  communicates  with  the  body  cavity.  The 
latter  is  divided  by  six  bilateral  mesenteries.  So  far  no 
trace  of  biradial  mesenteries  has  been  discovered  in  the 
young  Antipathes,  and  these  mesenteries  we  should 
expect  to  find .  if  the  group  were  reduced  descendants  of 
the  Hexactiniae  as  some  naturalists  maintain.  The 
young  Antipathes  sends  out  fleshy  prolongations  from 
the  basal  portion  of  its  body  and  these  bud  other  zoons,. 
thus  giving  rise  to  a  colony  (No.  192).  The  bases  of  all 
the  zoons  secrete  a  black  horny  stem  or  axis  (No.  193, 
A.  dissecta  D.  &  M.) ,  which  gives  rigidity  to  the  stalk. 
This  secretion  is  restricted  to  the  "foot"  of  the  zoons, 
the  body  walls  never  taking  part.  We  have  seen  that 
this  is  also  the  case  with  some  of  the  Alcyonaria,  a  group 
in  which  Antipathes  is  sometimes  placed.  The  posses- 
sion, however,  of  six  bilateral  mesenteries  seems  to  show 
relationship  with  the  Hexactiniae. 

Zoanfhtos  so  lander  i^ess.  (No.  194),  is  a  simple  colony, 
the  members  of  which  are  connected  by  stolons.  The 
arrangement  of  the  mesenteries  is  still  essentially  bi- 
lateral. 

In  Mammillifera  ?  (No.  195).  the  zoons  arise  from  a 
basal  membrane  and  are  of  about  the  same  height. 

Hexactiniae.  The  simple  members  of  this  group  are 
illustrated  by  Halcampa  chrys  ant  helium  Gse.  (No.  196), 
which  is  a  free-swimming  animal.  In  its  development  it 
passes  through  the  Edwardsia  stage  of  eight  bilateral 
mesenteries,  but  when  adult  it  possesses  twelve  biradia! 
mesenteries. 

The   Actiniae  next  to  be  described  are  bilateral  in  the 


1  This  organ  is  called  in  text  books  and  manuals  "oesophagus," 
"stomach,"  "stomodaeum."  According  to  Prof.  E.  B,  Wilson  it  is 
an  ectodermic  structure  and  has  nothing  to  do  with  the  stomach  — 
structurally  or  functionally.  It  is  homologous  with  a  stomodaeum, 
or,  what  is  more  probable,  with  a  fused  stomodaeum  and  procto- 
daeum.  We  have  called  it  simply  a  bag. 


128  SYNOPTIC    COLLECTION. 

early    stages   of  development,   but  afterward  develop   a 
radial  symmetry.1 

Actiniae.  It  is  now  pretty  well  established  that  the 
Actiniae  are  bisexual.  The  egg  of  our  common  sea 
anemone,  Metridium  marginatum  Ag.  (PI.  197,  figs,  i-io), 
leaves  the  parent  form  unfertilized.  This  is  not  the  case 
with  all  Hexactiniae,  the  embryo  of  Rhodactis  being  so  far 
developed  when  it  passes  into  the  water  as  to  possess  from 
two  to  four  mesenteries,  while  that  of  Aulactinia  possesses 
eight  or  twelve.  Fig.  i  is  an  immature  ovum  taken  from 
the  ovary.  The  nucleus  with  its  nucleolus  and  the  process 
extending  outward  at  one  pole  are  clearly  seen.  Figs.  2-6 
represent  the  segmentation  of  the  egg ;  fig.  7  is  the  young 
blastula ;  fig.  8,  an  optical  section  of  a  free-swimming 
blastula.  Some  of  the  embryos  at  this  stage  are  hollow 
and  seem  to  be  empty,  while  others  (fig.  9)  are  filled  with 
a  liquid  containing  scattered  cells.  Fig.  TO  illustrates  the 
formation  of  the  endoderm  by  delamination  of  the  inner 
ends  of  the  ectoderm  cells.  After  this  stage  ihe  mouth 
breaks  through,  making  an  opening  to  the  internal  cavity. 
The  young  Actinian  (PI.  198,  figs.  1-3  ;  the  vertical  line 
represents  the  height  of  the  anemone  when  expanded) 
is  a  single,  fleshy  animal.  The  mouth  is  surrounded  by  a 
limited  number  of  hollow  tentacles.  It  leads  into  the  in- 
ternal bag  which  communicates  with  the  body  cavity. 
The  latter  is  divided  first  by  four,  then  by  eight  mesen- 
teries which  arise  bilaterally.  There  is  no  indication  of  a 
skeleton  in  the  young  sea  anemone,  neither  is  there  so 
great  differentiation  in  the  histological  structure  of  the 
animal  as  in  more  specialized  Anthozoa.  For  these 
reasons,  and  because  the  mesenteries  arise  on  either  side 
of  the  median  plane  of  the  body,  producing  bilateral 
symmetry,  we  regard  the  Actinia  as  a  primitive  rather 
than  a  reduced  form.  When  the  animal  grows  older  the 
bilateral  arrangement  of  parts  gives  way  to  a  radial 

1Moseley,  Quart.  Journ.  Micr.  Sci.,  XXII,  1882,  p.  395. 


METAZOA COELENTERA.  129 

arrangement.  Thus  the  base  of  the  anemone  (PI.  198, 
fig.  3)  exhibits  a  small  number  of  biradial  partitions. 

Young  and  adult  stages  of  the  anemone  are  seen  in  the 
alcoholic  specimens  (No.  199).  The  cylindrical  body  is 
usually  attached  by  its  base  (No.  199),  although  it  has  the 
power  of  gliding  over  surfaces.  The  mouth  is  surrounded 
by  tentacles  (Nos.  199,  200)  which  can  be  drawn  in  and 
entirely  concealed.  The  mouth  is  open  and  more  or  less 
circular  in  the  alcoholic  specimens  (Nos.  199,  200),  but 
in  life  it  is  slit- like.  It  is  provided  with  two  siphono- 
glyphs.  In  the  living  animal  these  are  seen  to  be  lined 
with  long  cilia.  When  the  mouth  is  closed  the  central 
parts  come  together,  while  the  siphonoglyph  at  either  end 
is  open  so  that  a  current  of  water  can  be  kept  circulating 
through  the  body.  The  mouth  of  the  adult  opens  into 
the  flattened  internal  bag,  and  the  latter  into  the  body 
cavity,  which  is  divided  into  chambers  by  biradial  mesen- 
teries, seen  in  the  preparation  (No.  201).  At  each  end  of 
the  flattened  bag  there  is  a  pair  of  mesenteries  called 
"  directives."  Four  other  pairs  of  long  walls  reach  the 
central  bag,  making  six  pairs  of  primary  mesenteries. 
Besides  these  there  are  cycles  of  shorter  pairs,  the  num- 
ber depending  upon  the  age  of  the  anemone.  When 
mature  the  mesenteries  bear  the  long  convoluted  repro- 
ductive organs. 

The  mesenteries  are  not  arranged  symmetrically  and 
equally  distant  from  one  another,  as  might  be  inferred 
from  figures  often  given  in  textbooks.  In  a  collection  of 
twenty-one  anemones  sent  from  Beverly  bridge,  not  one 
showed  a  perfectly  symmetrical  arrangement.  In  nearly 
all,  six  or  eight  of  the  mesenteries  which  reached  the 
central  bag  were  bunched  closely  together,  while  the  re- 
maining ones  were  separated  from  these  by  a  greater  or 
less  distance.  One  specimen  had  four  biradial  pairs  and 
an  odd  one  ;  two  specimens  had  six  pairs  and  an  odd  one  ; 
another  was  found  with  seven  pairs  and  an  odd  one, 
while  still  another  had  eight  pairs. 


130  SYNOPTIC    COLLECTION. 

The  shorter  mesenteries  bear  long  filaments  which  are 
provided  with  thread  cells,  and  which  can  be  thrown  out 
of  the  mouth  and  through  openings  in  the  body  wall. 

Actiniae  generally  reproduce  in  the  manner  already  de- 
scribed, but  occasionally  they  increase  by  budding  and 
by  fission.  No.  202  is  a  rare  specimen  of  Metridium 
which  has  two  mouths  in  the  oral  disc.  When  a  constric- 
tion takes  place  between  these  two  and  the  oral  disc 
divides,  the  method  of  fission  is  illustrated,  and  two  ani- 
mals are  produced  which  in  No.  203  have  not  separated. 

There  are  a  number  of  different  genera  of  Actiniae  in 
the  Collection  illustrating  interesting  features. 

Anemonia  sulcata  (No.  204),  is  remarkable  for  its  short 
body  and  its  numerous  large,  long  tentacles  which  float  in 
the  water  like  hungry  food  catchers. 

The  slit-like  mouth  with  thickened  lips  peculiar  to 
anemones  is  well  seen  in  Adamsia  rondeleti  (No.  205). 
This  anemone  has  the  habit  of  fastening  itself  to  the 
inner  part  of  the  opening  of  a  Gastropod  shell,  as  shown 
in  No.  205  ;  the  bases  of  the  different  animals  often  touch 
one  another,  but  there  is  no  organic  connection.  One 
species  of  this  genus  (A.  palliata)  is  found  as  a  messmate 
on  the  back  of  the  crab,  Pagurus  prideauxi. 

Anthea  cereus  Johnst.  (No.  206),  has  little  power  of 
drawing  in  its  tentacles,  which  are  placed  at  the  junction 
of  the  body  wall  and  the  oral  disc.  The  exquisite  color- 
ing of  Actiniae  is  illustrated  by  all  the  glass  models  of 
these  animals  but  especially  by  this  species  of  Anthea. 

Bunodes  crispa  Ehr.  (No.  207),  is  a  rare  anemone.  The 
surface  of  the  upper  part  of  the  body  has  many  warts 
which  are  used  as  suckers  for  mooring  the  animal  or  for 
the  attachment  of  foreign  particles.1  There  is  an  indefi- 
nite number  of  retractile  tentacles,  some  small  and  others 
so  large  and  long  that  they  look  like  grasping  organs. 
Suctorial  warts  similar  to  those  of  Bunodes  are  also  found 
in  Tealia  crassicornis  Mull.  (No.  208). 

'Proc.  Roy.    Dublin  Soc.,  VI,  1889,  p.  315. 


METAZOA COELENTERA.  4        131 

The  body  of  Phymactis  florida  Drayton  (No.  209),  is 
much  shorter  than  that  of  Metridium ;  its  mouth  is  ele- 
vated above  the  oral  disc  and  surrounded  by  short  tenta- 
cles. 

Phyllactis  punctata  Couthouy  (No.  210),  is  a  large 
Actinian  in  which  the  inner  tentacles  are  similar  to  those 
of  our  common  sea  anemone,  while  the  outer  ones  are  like 
fluted  lobes  edged  with  green.  These  lobes  sometimes 
adhere  together  nearly  their  whole  length.  This  Actinian 
is  found  buried  up  to  its  disc  in  sand.  According  to  Dana 
this  creature  crawled  on  glass  by  means  of  its  outer  lobed 
tentacles. 

Biddium  parasiticum  Ag.  (PI.  211,  figs,  i,  2,  natural 
size),  is  interesting  since,  unlike  most  Actiniae,  it  pos- 
sesses an  anus  at  the  posterior  end  of  its  body.  It  is 
found  in  the  mouth-folds  of  the  medusa,  Cyanea  arctica 
Per.  &  Less.  The  body  is  long  and  ribbed  from  one  end 
to  the  other.  Besides  the  longitudinal  markings  there  are 
many  transverse  wrinkles.  Fig.  i  shows  the  body  con- 
tracted and  the  anus  open.  The  terminal  opening  in  five 
tentacles  is  seen,  two  are  closed,  and  one  is  turned  from 
the  observer.  In  fig.  2  the  body  is  expanded  and  the 
anus  closed ;  the  twelve  tentacles  are  visible.  Fig.  3  is 
an  enlarged  drawing  of  the  posterior  portion  of  the  body, 
showing  the  terminal  anus  and  the  rows  of  minute  openings 
which  radiate  from  it. 


ANTHOZOA. 

MADREPORARIA. 

The  Madreporaria  may  be  grouped  into  the  Aporosa  or 
Imperforata,  the  Fungidae,  and  the  Perforata.  It  must 
be  borne  in  mind,  however,  that  there  are  no  sharp  divi- 
sion lines  between  these  groups.  The  time  will  doubtless 
come  when  the  ancient  imperforate  Madreporaria  will  be 
distributed  as  ancestral  forms  among  the  different  families 


132  SYNOPTIC    COLLECTION. 

of  corals  living  to-day,  but  at  present  so  much  uncertainty 
exists  in  regard  to  their  true  relationships  that  we  consider 
them  as  ancestors  of  the  whole  group  of  Madreporaria. 

The  skeleton  of  the  Madreporaria  is  not  spicular,  like 
that  of  the  Alcyonaria,  but  it  is  a  hard,  solid  secretion  of 
carbonate  of  lime.  The  theca  in  the  Imperforata  is 
not  pierced  by  openings  or  pores,  so  that  there  is  no 
system  of  canals  connecting  different  corallites.  In  the 
Madreporaria  Fungidae  the  young  are  imperforate  and  the 
adult  perforate,  while  in  the  Perforata  there  are  numerous 
pores  both  in  the  young  and  the  adult  stages,  and  the 
corallites  are  in  communication  with  one  another. 

The  structure  of  these  three  groups  is  essentially  similar 
to  that  of  the  sea  anemones  or  Hexactiniae  just  described, 
with  the  exception  that  the  Madreporaria  possess  a  skele- 
ton. The  formation  of  the  skeleton  has  been  studied  by 
many,  notably  by  von  Koch1  and  Ogilvie.'2  The  larva 
begins  to  form  a  skeleton  after  it  is  attached.  The  first 
rudiment  is  a  disc  perforated  in  the  center  which  after- 
ward becomes  entire.  This  disc  is  between  the  ectoderm 
of  the  larva  and  the  rock  to  which  the  latter  is  attached, 
and  is  a  secretion  of  the  ectoderm.  It  cannot  be  formed 
by  either  the  endoderm  or  the  mesoderm,  since  it  is  sepa- 
rated from  these  layers  by  the  ectoderm.  In  time  there 
appear  radial  ridges  or  upward  foldings  of  the  basal  disc. 
The  ectoderm  in  these  foldings  secretes  carbonate  of  lime 
and  thus  limy  septa  are  formed.  In  one  genus  observed  3 
there  were  twelve  mesenteries  and  twelve  septa,  six  in  the 
chambers  between  each  biradial  pair  of  mesenteries 
(entosepta)  and  six  others  in  the  chambers  between  two 
adjoining  biradial  pairs  (exosepta).  In  the  younger  zoons 
there  were  twelve  mesenteries  and  only  six  septa,  and 

1Mitth.  d.  Zool.  Stat.  Neapel,  III,  1882.  Morph.  Jahrb.,  V,  VI, 
VIII.  See  also  Fowler,  Quart.  Journ.  Micr.  Sci.,  XXV,  1885. 

2Proc.  Roy.  Soc.  London,  LIX,  1895;  Phil.  Trans.  Roy.  Soc. 
London,  B,  CLXXXVII,  1896. 

3  Madreporia  variabilis. 


METAZOA  —  COELENTEPA.  133 

these  were  the  entosepta.  In  time,  according  to  von 
Koch,  the  septa  fork  at  their  ends  and  later  these  ends 
fuse  to  form  the  cups  or  thecae.  According  to  Lacaze- 
Duthiers  the  theca  arises  as  a  ring-like  thickening  of  the 
base  entirely  independent  of  the  septa.1  Sometimes  the 
central  ends  of  the  septa  fuse  and  form  the  columella. 

While  these  changes  are  taking  place,  the  ectoderm  at 
the  free  margin  of  the  young  coral  animal  secretes  lime 
whereby  the  epitheca  is  formed.  This  is  a  thin  imperfo- 
rate  layer  which  is  originally  free  from  the  theca  but  which 
secondarily  fuses  with  it. 

Many  of  the  imperforate  Madreporaria  occur  in  the 
early  geologic  formations.  The  structure  of  the  skeleton 
of  these  ancient  corals — also  called  Rugosa  and  Tetraco- 
ralla — does  not  differ  from  that  of  recent  corals.  The 
tetrameral  symmetry  (or  having  the  parts  in  multiplies  of 
four)  peculiar  to- many  of  them  is  not  a  constant  charac- 
ter, and  a  hexameral  symmetry  is  not  by  any  means  char- 
acteristic of  recent  corals.2 

The  relationship  between  these  ancient  and  modern 
forms  causes  them  to  be  placed  together  under  the  head 
of  the  Madreporaria  Aporosa. 

It  is  probable  that  the  earliest  ancestors  of  our  coral 
animals  were  disc-like  in  form,  for  the  reason  that  this  is 
the  first  condition  of  the  skeleton  of  existing  species.  In 
time  this  disc-shaped  coral  probably  became  cup-  or  horn- 
shaped,  —  a  very  common  form  among  ancient  species. 

The  primitive  disc-shaped  ancestors  are  not  known  with 
certainty,  so  that  we  must  pass  to  the  cup-shaped  forms; 
of  these  there  are  a  number  in  the  Collection. 

Cystiphyllum  americanum  E.  &  H.  (No.  212),  has  septa 
that  are  only  slightly  developed,  being  indicated  by  mere 
ridges.  The  coral  is  vesicular  throughout  but  towards 

1  For  a  discussion  of  these  views,  see  Fowler,  Quart.  Journ.  Micr. 
Sci.,  XXV,  1885. 

2  Treatise  on  Zoology,  ed.  by  E.  Ray  Lankester,  Part  2,  1900, 

p.  70. 


134  SYNOPTIC    COLLECTION. 

the  base  the  vesicles  are  larger  and  there  is  a  tendency 
towards  forming  tabulae.  During  periods  of  rest  or  com- 
parative inactivity  the  vesicular  mass  becomes  more  or 
less  dense  and  apparently  a  cup  is  formed.  For  this 
reason  there  is  a  succession  of  cups,  representing  not  differ- 
ent zoons  that  have  budded  but  different  degrees  of  activ- 
ity in  forming  the  skeleton.  If  each  were  a  bud,  one 
ought  to  find  the  epitheca  extending  down  into  the  cup, 
which  is  not  the  case.  Still  there  are  some  specimens 
which  appear  to  be  made  of  the  skeletons  of  two  zoons, 
and  as  the  epitheca  is  continued  on  the  outside  it  is  diffi- 
cult to  give  an  explanation.  In  most  specimens  the  epi- 
theca is  worn  off,  but  when  preserved  it  shows  distinct 
concentric  ridges. 

The  operculated  corals  seem  to  be  related  to  the  Cysti- 
phyllidae  although  they  are  more  specialized  in  structure. 

One  of  the  forms  whose  affinities  have  so  far  baffied 
naturalists  is  the  Cretaceous  Barrettia  monilifera  Wood- 
ward (PI.  213,  fig.  i,  greatly  reduced).  Its  shape  and 
general  appearance  would  place  it  with  Calceola  and  the 
other  operculated  corals,  but  in  structure  it  is  different 
from  any  fossil  so  far  discovered.  According  to  Wood- 
ward, who  first  described  the  specimen  (1862),  it  belongs 
to  the  Rudistae,  a  group  of  molluscs  to  which  also  Hip- 
purites  and  Radiolites  (PI.  428,  figs,  i,  2)  belong.  This 
view  was  based  upon  the  fact  that  in  Woodward's  speci- 
mens Barrettia  possessed  a  bivalve  shell.  According  to 
Whitfield  (1897)  Barrettia  is  more  nearly  related  to  corals 
than  to  molluscs. 

The  visceral  cavity  occupied  the  center  (PI.  213,  fig.  2, 
longitudinal  section  ;  fig.  3,  cross  section).  Below,  it  was 
divided  by  transverse  partitions  (fig.  4).  Radiating  from 
the  central  cavity  were  lines  of  vertical  tubes  or  monili- 
form  rays  (figs.  3,  4),  and  close  by  it  was  a  larger  tube 
divided  by  transverse  walls  (fig.  4  a). 

The  spaces  between  the  radiating  rows  of  tubes  were 
filled  with  four-walled  tubes  which  were  also  divided 


.METAZOA COELENTERA.  135 

horizontally  by  walls  (fig.  5,  summit  view;  fig.  6,  vertical 
section).  The  moniliform  rays  may  be  seen  in  fig.  5,  in 
the  ridges  between  the  rows  of  four-walled  cells. 

The  specimens  described  by  Whitfield  (figs.  4-6) 
showed  no  upper  valve  ;  in  fact,  there  was  nothing  to 
indicate  a  molluscan  character  in  the  genus,  such  as  is 
plainly  seen  among  the  Rudistae.  At  the  same  time 
the  genus  is  different  from  any  of  the  operculated  corals, 
although  it  is  placed  in  this  group  provisionally  until  more 
perfect  specimens  can  be  obtained. 

The  single  form  Zaphrentis  (No.  214)  of  the  family 
Zaphrentidae  has  a  bilateral  arrangement  of  the  septa. 
The  "pit"  .or  fossula  usually  contains  a  shorter  septum. 
Here  were  probably  the  mesenteries  that  bore  the  repro- 
ductive organs.  The  septa  are  contorted  at  the  center 
and  the  tabulae  are  not  clearly  defined,  while  there  is 
scarcely  any  vesicular  structure. 

Cyathaxonia  prolifera  McChes.  (No.  215),  is  a  single 
form  with  septa  arranged  radially  and  a  central  projecting 
columella.  The  young  Cyathaxonia  has  an  epitheca  on 
the  end,  which  is  very  delicate,  so  that  it  is  usually  worn 
off  and  is  seldom  seen  in  fossils. 

Heliophyllum  halliY,.  &  H.  (No.  216),  is  an  illustration 
of  a  single  Cyathophylloid  coral.  It  has  the  form  of  a 
flaring  shallow  cup.  The  epitheca  is  seen  on  the  outside, 
while  the  vertical  septa  are  distinctly  seen  within  the  cup 
and  are  radially  arranged.  Between  the  septa  on  the 
outer  side  there  is  more  or  less  vesicular  structure  ;  the 
tabulae  cannot  be  made  out  in  the  specimens  but  the  ridges 
on  the  septa  are  plainly  seen  and  appear  like  cross  bars 
between  the  septa. 

Acervularia  ananas  Linn.  (No.  217),  is  a  colonial  form 
consisting  of  many  coral  animals  that  lived  closely  to- 
gether. Here  there  is  an  external  epitheca.  The  septa 
extended  to  the  central  bag,  and  below  this  organ  to  the 
center.  They  are  indicated  on  the  surface  of  the  coral 
by  radiating  lines.  The  vesicular  structure  has  largely 


136  SYNOPTIC    COLLECTION. 

disappeared.  Budding  takes  place  from  the  edge  of  the 
cup  and  a  spreading  form  results. 

Lithostrotion  canadense  Castelnau  (No.  218),  is  another 
colonial  form  in  which  the  vertical  septa  and  columella 
are  clearly  shown  ;  the  tabulae  are  seen  on  a  broken  sur- 
face. 

Turbinolia  sessilis  Blainv.  (No.  219),  of  the  family 
Turbinolidae  is  a  single  coral  of  more  recent  date.  It  has 
a  columella  projecting  in  the  center  (although  not  shown 
in  the  specimen)  and  the  septa  are  arranged  radially. 

A  single,  deep-sea  form  is  Caryophyllia  (No.  220, 
C.  smithi  var.  castanea).  This  is  a  most  instructive  speci- 
men, for  it  exhibits  the  striking  similarity  between  a  sea 
anemone  and  a  coral  animal.  The  epitheca  is  formed 
around  the  lower  part  of  the  body.  The  septa  of  the 
skeleton  are  numerous  and  the  larger  ones  predominate. 
In  the  center  is  a  twisted  columella. 

Oculina  (No.  221),  is  one  of  the  irregular  branching 
corals  with  rounded  tips.  The  corallites  are  distinct, 
with  the  coenenchyma  showing  plainly  near  the  base  but 
almost  wholly  disappearing  at  the  ends  of  the  branches. 

The  colonial  Pocillopora,  represented  by  the  large, 
handsome  specimen  on  the  lowest  shelf  of  the  erect  por- 
tion of  Section  4  (No.  222,  P.  nobilis  Verr.),  has  stout 
obtuse  branches.  As  in  Oculina,  the  corallites  on  the 
sides  of  the  branches  are  separated  by  the  coenenchyma, 
but  at  the  ends  they  are  crowded  closely  together.  The 
tabulae  show  finely  in  a  side  view.  The  columella  is 
sometimes  well  developed  but  in  other  specimens  poorly. 
This  coral  increases  by  budding  and  rarely  by  fission. 
The  thecae  in  Pocillopora  are  divided  by  a  long  median 
septum  ;  the  other  septa  in  this  genus  and  in  the  beauti- 
ful Seriatopora  (No.  223,  see  lowest  shelf),  are  minute, 
and  in  the  latter  genus  the  tabulae  are  scarcely  visible. 

The  family  Astraeidae  is  a  large  one,  including  many 
genera.  Antill/a  explanata  Pourtales  ( =  Lithophyllia 


METAZOA COELENTERA.  1 37 

cubensis^  M.-Ed.  &  H.)  (PI.  224),  is  one  of  the  more 
generalized  members  of  the  family.  It  is  disc-shaped 
(PI.  224,  fig.  i)  like  the  original  basal  plate  of  the 
Madreporian  skeleton.  Antillia  offers  an  illustration  of 
the  co-existence  of  the  epitheca  and  theca  in  one  zoon. 
The  epitheca,  which  is  well  developed  in  this  species,  is 
shown  in  fig.  2,  and  also  the  central  small  area  of  attach- 
ment. 

Cladocora  caespitosa  Lam.  is  seen  in  the  glass  model 
(No.  225).  At  the  left  is  a  single  zoon  much  enlarged^ 
and  just  back  of  it  is  the  colony.  The  theca  is  present 
and  the  ridges  on  the  outside  correspond  to  the  septa. 
Vesicular  structure  exists  though  in  small  quantities,  and 
the  epitheca  is  only  slightly  developed. 

The  little  Astrangia  danae  Ag.  (No.  226  ;  No.  227,. 
skeletons  attached  to  a  stone),  is  the  only  coral  living  in 
our  New  England  waters.  It  is  a  colonial  form  and  the 
corallites  are  connected  by  the  coenenchyma.  The  septa 
unite  at  the  center  in  a  columella  and  there  is  no  epitheca. 

There  are  many  corals,  like  Mussa,  Manicina,  and  the 
like,  that  increase  by  a  process  of  incomplete  fission  which 
results  in  winding  furrows  with  such  indistinct  thecae 
that  often  the  limits  of  the  different  skeletons  cannot  be 
made  out  with  certainty. 

The  septa  in  Mussa  tenuidentata  M.-Ed.  &  H.  (No. 
228),  are  large  and  toothed  and  the  columella  is  spongy. 
In  some  specimens  the  epitheca  is  slightly  developed  and 
in  others  it  does  not  exist.  According  to  Martin  Duncan2 
the  young  of  this  genus  cannot  be  distinguished  from 
simple  Astraeidae  of  the  Antillia  type.  Mussa  increases 
by  fission,  as  we  have  said,  and  the  process  is  often 
illustrated  in  one  specimen  where  the  original  circular 
corallite  may  be  found,  and  also  more  advanced  corallites 
that  are  elongated,  constricted,  and  nearly  or  wholly 
divided. 


1  Quart.  Journ.  Geol.  Soc.  London,  LI,  1895,  p.  259. 
2Journ.   Linn.  Soc.  London,  Zool.,  XVIII,  1884,  p.  83. 


138  SYNOPTIC    COLLECTION. 

Manicina  is  interesting  for  the  reason  that  it  is  a  rapid 
swimmer  when  young,  fixed  by  a  pedicel  when  mature, 
and  free  again  when  old.  In  developing,  the  stage 
with  eight  mesenteries  is  followed  in  a  day  or  two  by  the 
stage  with  twelve.1  The  skeletons  (No.  229)  show 
different  stages  of  growth,  the  colony  never  becoming 
much  larger  than  the  largest  specimen. 

Euphyllia  gracilis  Dana  (No.  230),  forms  small  colo- 
nies. The  thecae  in  this  genus  are  circular,  compressed, 
and  sometimes  meandering. 

The  same  method  of  reproduction  is  illustrated  by  the 
massive  brain  coral,  Diploria  cerebriformis  M.-Ed.  &  H. 
(No.  231),  which  grows  to  a  great  size  and  which  repre- 
sents the  skeletons  of  a  vast  number  of  coral  animals. 

Favia  (No.  232)  is  a  hemispherical  colonial  form  in 
which  the  corallites  are  united  and  the  septa  are  toothed. 
The  columella  is  spongy  and  an  epitheca  sometimes  ex- 
ists. 

Orbicella  annularis  Dana  (No.  233),  is  also  hemispheri- 
cal in  shape  and  the  new  buds  arise  in  the  spaces  between 
the  corallites. 

The  corallites  in  Galaxea  fascicularis  Oken  (No.  234), 
project  from  the  surrounding  coenenchyma.  Each  is 
marked  by  striae  which  indicate  the  septa.  The  latter 
are  distinct  and  the  longer  ones  reach  to  the  columella 
which  does  not  project  upward.  This  genus  increases  by 
budding  from  the  walls  of  the  corallites  and  also  from  the 
basal  coenosarc  that  extends  between  the  corallites.  The 
coral  takes  on  a  foliaceous  shape  in  Agaricia  agaricitcs 
E.  &  H.  (No.  235).  The  columella  is  present  but  the 
septa  are  not  numerous.  Pachyseris  luevicollis  E.  &  H. 
(No.  236),  is  a  related  form. 

IH.  V.  Wilson,  Journ.  of  Morph.,  II,  No.  2,  1888,  p.  191. 


METAZOA COELENTERA.  139 


MADREPORAKIA  FUNGIDAE. 

Palaeocyclus  (No.  237)  and  Cyclolites  (No.  237)  are 
mushroom-corals  which  antedate  our  present  Fungia. 
From  a  study  of  the  early  stages  of  the  latter,  however, 
it  is  probable  that  all  these  coral  animals  arose  from  a 
cup-shaped  rather  than  a  mushroom-shaped  ancestor.  It 
may  be  that  a  still  more  remote  ancestor  was  disc-shaped, 
as  we  have  already  said,  and  that  the  Madreporaria 
Fungidae,  which  possess  a  similar  plate-like  form,  are  its 
specialized  and  reduced  descendants. 

Nothing  is  known  of  the  young  stages  of  Palaeocyclus 
and  Cyclolites.  The  adult  is  disc-shaped  and  the  epitheca 
is  confined  to  the  base.  The  septa  rise  as  so  many  walls 
of  varying  length  from  the  basal  plates. 

Turning  to  the  development  of  Fungia  we  find  that  the 
parent  stock  is  attached  (PI.  239,  fig.  i).  It  is  cup-shaped 
with  a  distinct  theca,  while  the  cavity  of  the  cup  is  divided 
into  chambers  by  septa.  In  this  stage  it  resembles  Caryo- 
phyllia.  In  time  the  oral  disc  increases  in  size  at  the 
expense  apparently  of  the  thecal  portion  (fig.  2).  The 
growth  is  lateral,  until  at  last  the  young  Fungia  separates 
from  the  parent  stock  a  short  distance  below  the  disc 
where  the  dark  line  is  seen  in  fig.  3.  When  set  free  the 
Fungia  has  an  opening  beneath,  where  it  was  fastened, 
but  this  quickly  fills  up  by  a  secretion  of  carbonate  of 
lime.  The  scar  is  seen  in  young  specimens  (No.  240). 
The  Fungia  is  henceforth  free  (PI.  239,  figs.  4,  5)  with 
only  slight  evidences  on  the  lower  side  of  its  attachment, 
and  these  finally  disappear  (fig.  6) .  The  parent  stock 
continues  to  bud  forth  other  animals  which  likewise  become 
detached.  According  to  Semper1  the  parent  stock  is 
comparable  to  the  strobila  of  the  Discophora  and  exhibits 
a  true  alternation  of  generations. 

1  Zeitschr.  f.  wiss.  Zool.,  XXII,  1872,  p.  267. 


140  SYNOPTIC  COLLECTION; 

Bourne  1  objects  to  the  use  of  the  word  strobila  which 
was  originally  applied  to  the  dividing  parent  stock  of 
Aurelia.  This  is  essentially  different  from  the  bud-pro- 
ducing parent  stock  of  Fungia,  and  since  it  is  objection- 
able to  use  the  same  name  for  two  very  different  phe- 
nomena Bourne  uses  nurse  stock  for  the  fixed  parent  of 
Fungia. 

Rarely  a  specimen  is  found  with  the  parent  stock 
attached  to  it,  as  seen  in  No.  240.  This  stock  was  cov- 
ered over  with  limy  deposits  by  the  growing  animal,  and 
these  had  to  be  removed  by  acid  when  the  original  stock 
form  was  exposed  with  its  cup  like  shape  and  internal 
walls. 

The  central  or  younger  portions  of  the  adult  Fungia 
(No.  241)  are  imperforate  but  the  older  portions  are 
perforated.  The  septa  increase  in  number  from  the  cen- 
ter outwards,  as  is  well  shown  in  No.  241. 

MADREPORARIA  PERFORATA. 

The  simpler  members  of  the  Madreporaria  Perforata 
are  Dendrophyllia  (No.  242)  and  Coenopsammia.  (No. 
243,  C.  tenuilamillosa  Verr.)  .  The  former  is  a  branching 
coral  and  the  latter  a  low,  spreading  form.  The  corallites 
in  both  are  large  and  the  septa  are  distinct.  Buds  grow 
from  the  sides  of  the  corallites  but  a  massive  colony  never 
results. 

Astroides  calycularis  Pallas  (No.  244),  is  a  simple  col- 
ony in  which  the  corallites  are  packed  closely  together 
and  rise  to  about  the  same  height.  This  was  one  of  the 
species  on  which  von  Koch  made  his  valuable  investiga- 
tions upon  the  formation  of  the  coral  skeleton. 

The  Madrepore  coral  (Nos.  245-248),  is  a  typical 
example  of  the  Perforata.  The  pores  may  be  finely  seen 

1  Quart.  Journ.  Micr.  Sci.,  XXVII,  1887,  p.  294. 


METAZOA COELENTERA.  141 

when  a  specimen  is  held  to  the  light.  No.  247  is  a  verti- 
cal section  of  this  coral  that  exhibits  these  characteristic 
openings  by  means  of  which  the  zoons  communicate  with 
one  another.  This  coral  assumes  different  shapes  ;  it  is 
branching  (No.  245,  in  more  natural  condition  than  No. 
248,  which  has  been  bleached),  and  it  is  flat  and  encrust- 
ing (No.  246,  Madrepora  convexa  Dana).  The  long  septa 
reach  the  center,  where  there  is  a  more  or  less  spongy 
columella.  The  walls  of  the  corallites  are  not  distinct 
from  the  coenenchyma,  which  is  largely  developed  ;  and 
the  epitheca  is  wanting. 

Budding  takes  place  from  the  central  and  parent  form 
which  has  remarkable  vitality,  and  also  from  the  sides  of 
other  corallites  which  are  larger  and  longer  than  most  of 
their  neighbors.  The  skeleton  of  the  central  parent  zoon 
is  seen  cut  in  two  in  No.  247.  In  healthy  condition  the 
ends  of  the  branches  of  Madrepore  are  always  pointed, 
but  in  No.  248  there  are  a  number  of  diseased  tips  with  a 
puffed  out,  swollen  appearance. 

The  corallites  in  Porites  (No.  249,  P.  claviaria  Lam.,  a 
branching  form;  No.  250,  vertical  section  of  P.  astrae- 
oides  Lam.,  a  rounded  form)  are  crowded  thickly  together 
on  a  level,  with  no  intervening  coenenchyma.  The  septa 
are  imperfect  and  spinous ;  there  are  no  tabulae  and  the 
columella  is  small.  The  coral  is  more  dense  than  in 
Madrepore  (compare  No.  247  with  No.  250),  and  there 
is  no  large  parent  zoon. 

We  have  attempted  to  show  that  the  Coelentera  as 
represented  by  the  Hydrozoa  and  Anthozoa  have  a  defi- 
nite form  and  a  body  cavity  all  the  parts  of  which  are  in 
communication  with  one  another.  Beginning  with  a  primi- 
tive Palaeozoic  ancestor  we  pass  to  living  free-swimming 
hydroids  that  have  a  direct  development,  the  hydroid 
growing  into  a  medusa. 

Again,  free  swimming  hydroids  become  attached  and 
colonies  arise  by  budding.  These  produce  free  medusae 


142  SYNOPTIC    COLLECTION. 

whose  eggs  develop  into  fixed  or  stationary  hydroids,  there- 
by illustrating  the  process  of  indirect  development  and  the 
alternation  of  generations. 

The  eggs  of  other  medusae  develop  into  medusae,  skip- 
ping altogether  the  hydroid  stage  and  illustrating  the  proc- 
ess of  accelerated  development. 

Lastly,  certain  hydroids  whose  ancestors,  we  have 
reason  to  believe,  produced  free  medusae  have  taken  on 
such  reduced  characters  it  seems  probable  that  the  me- 
dusa stage  is  omitted  in  their  ontogeny,  and,  if  so,  they 
illustrate  suppressed  development. 

Acceleration  in  development  is  shown  by  the  Disco- 
phora,  while  specialization  of  structure  and  function,  re- 
sulting in  complex  colonial  life,  is  characteristic  of  the  Si- 
phonophora. 

The  Ctenophora  constitute  one  of  those  interesting  syn- 
thetic types  whose  relationships  reach  out  beyond  the 
limits  of  the  Hydrozoa,  beyond  even  the  boundaries  of 
the  Coelentera,  to  the  subkingdom  of  the  Echinoderms. 

The  ancestors  of  the  Alcyonarian  branch  of  the  Antho- 
zoa  are  illustrated  by  a  series  of  forms  which  show  most 
admirably  the  gradual  transition  from  the  primitive  and 
simple  to  the  secondary  and  complex. 

The  living  Alcyonaria  have  in  addition  to  what  the  Hy- 
drozoan  possesses,  an  internal  bag  and  a  body  cavity 
divided  into  chambers  by  eight  bilateral  mesenteries. 
Their  skeleton  is  made  of  spicules  and  is  chiefly  a  secre- 
tion of  the  ectoderm  of  the  basal  membrane  of  the  zoons. 

The  Zoantharia  likewise  have  an  internal  bag  and  in 
youth  a  body  cavity  divided  by  eight  bilateral  mesenteries, 
but  in  maturity  this  cavity  is  divided  by  numerous  bira- 
dial  mesenteries. 

The  skeleton  of  the  Madreporaria  is  a  solid  secretion  of 
the  ectoderm  and  consists,  speaking  generally,  of  a  basal 
disc  and  a  theca  with  true  septa. 

The  processes  of  reproduction  —  budding  and  fission 
—  and  the  influence  of  physical  forces  have  brought  about 


METAZOA COELENTERA.  143 

a  great  variety  in  form,  but  through  this  extreme  diversity 
the  fundamental  type  of  structure  remains  the  same. 

The  subkingdom  of  Vermes  or  Worms  is  placed  next 
the  Coelentera  by  many  authorities,  and  the  larvae  of  cer- 
tain worms  are  considered  as  the  nearest  approach  to  the 
ancestral  forms  from  which  all  the  remaining  invertebrates 
and  also  the  vertebrates  have  descended. 

There  is  a  resemblance,  speaking  broadly,  between  the 
larvae  of  echinoderms,  molluscs,  and  worms,  but  this  sim- 
ilarity may  be  due  to  inheritance  from  some  pre-Cam- 
brian  ancestor  from  which  the  three  branches  have  devel- 
oped along  different  lines.  When  one  considers  the 
varied  and  extreme  specializations  of  worms ;  the  articu- 
late plan  of  structure  differing  so  essentially  from  the  ra- 
diate plan  ;  the  greatly  developed  muscular  system  and 
the  complex  excretory  and  reproductive  organs ;  the  large 
number  of  extremely  reduced  forms,  one  finds  it  easier  to 
place  the  worms  among  the  more  specialized  and  the  ar- 
ticulated animals  than  next  to  the  comparatively  simple 
Coelentera. 

The  Echinoderms,  on  the  other  hand,  are  pre-eminently 
radiate  organisms,  and  in  many  ways  they  possess  char- 
acters in  common  with  the  Coelentera. 


METAZOA —  ECHINODERMA.  145 

ECHINODERMA. 

Sections  5,  6. 

CYSTOIDEA. 

Most  palaeontologists  consider  the  Cystoidea  as  the 
Palaeozoic  ancestors  of  the  Echinoderms,  while  embryolo- 
gists  hold  that  this  view  is  not  supported  by  facts.  Ac- 
cording to  Bury1  there  is  not  the  slightest  embryological 
evidence  that  the  Echinoderms  have  passed  through  a 
stage  in  which  they  are  fixed  by  the  aboral  pole,  like  the 
Cystoids.  He  goes  on  to  say,  "  Nevertheless,  almost  all 
embryologists,  apparently  out  of  deference  to  palaeonto- 
logical  conclusions,  have  thought  it  necessary  to  assume 
that  ontogeny  is  misleading,  and  that  a  period  of  fixation 
really  did  take  place  of  which  all  traces  have  since  disap- 
peared. Now  this  involves  us  in  a  question  of  fundamen- 
tal importance.  If  palaeontologists  have  really  proved 
beyond  any  reasonable  doubt  that  the  Echinozoa  are  de- 
rived from  fixed  ancestors,  then  ontogeny  is  misleading; 
but  if  it  is  misleading  to  such  an  extent  as  to  obliterate 
all  traces  of  a  process  of  such  immense  importance,  I  for 
my  part  do  not  see  how  we  can  trust  it  in  other  particu- 
lars, and  those  who  rely  upon  it  for  indications  of  phylo- 
genetic  history  had  better  reconsider  their  position." 
Professor  Bury  then  takes  up  the  question  at  length  from 
the  embryological  point  of  view  and  deduces  reasons  for 
considering  that  the  ancestors  of  Echinoderms  were  unat- 
tached forms. 

It  has  been  shown  by  Hyatt  and  other  investigators  that 
it  may  be  possible  for  all  traces  of  an  ancestral  structure 
to  be  lost,  and  still  the  ontogeny  of  the  individual  be  abso- 

1  Metamorphosis  of  Echinoderms.  Quart.  Journ.  Micr.  Sci.,  n.  s., 
XXXVIII,  1895,  p.  93. 


146  SYNOPTIC    COLLECTION. 

lutely  luminous  with  the  light  it  throws  upon  the  phylo- 
genetic  history  of  its  group.  So  far  from  being  mislead- 
ing, such  an  ontogeny  is  the  normal  and  inevitable  result 
of  the  operation  of  the  law  of  acceleration  in  development 
by  which  adult  characters  are  inherited  earlier  and  earlier 
in  the  life  of  the  individual,  until  it  may  be  they  appear  in 
the  embryo  only,  and  finally  disappear  altogether. 

According  to  A.  Agassiz1  the  Cystoids  and  Blastoids 
represent  among  fossil  Echinoderms  the  nearest  approach 
we  have  yet  discovered  to  the  imaginary  prototype  of  the 
subkingdom  of  spiny-skinned  animals. 

The  characters  possessed  by  the  living  Echinoderma  are 
such  that  they  can  be  explained  satisfactorily  only  by 
supposing  that  these  animals  are  the  descendants  of 
attached  forms.  It  may  be  possible,  as  already  suggested, 
that  the  ancestors  of  the  attached  forms,  living  in  some 
remote  pre-Cambrian  age,  were  free-swimming,  and  that 
these  free-swimming  adults  are  represented,  with  few  or 
many  modifications,  by  the  larvae  of  existing  Echino- 
derms, molluscs,  and  worms.  Be  this  as  it  may,  the  fact 
is  pretty  well  established  that  our  present  free-moving 
Echinoderms  are  directly  descended  from  fixed  or  sta- 
tionary ancestors. 

One  of  the  simplest  Cystoids  is  Aristocystis  (PI.  251, 
figs,  i,  2,  A.  bohemicus  Hkl.).  Here  we  have  a  body  pro- 
tected by  many  calcareous  plates  placed  together  irregu- 
larly. It  was  attached  by  its  base  (fig.  2),  which  was 
surrounded  by  more  regular  plates ;  as  yet  no  stem  had 
developed.  The  slit-like  mouth  was  on  the  upper  side 
(fig.  3,  m),  and  at  one  side  was  the  anus  (fig.  3,  a) 
closed  by  a  pyramid  of  plates.  Between  these  two  open- 
ings there  was  a  pore,  now  thought  to  be  the  genital  pore 
(fig.  3,  g).  Near  the  mouth  there  was  still  another  open- 
ing supposed  to  be  for  respiration  and  called  a  hydropore 
(fig.  3,  h).  In  this  genus  there  were  no  specialized  areas 

1  Proc.  Amer.  Assoc.  Adv.  Sci.,  XXIX,  1880,  p.  411. 


METAZOA  —  ECHINODERMA.  147 

of  plates  known  as  food  grooves  or  ambulacra,  and  no 
arms  extended  from  the  body. 

Another  primitive  form  was  Lichenocrinus  dyeri  Hall 
(PI.  252,  figs.  1-4).  Little  is  positively  known  in  regard 
to  this  genus,  and  it  is  only  on  account  of  the  structure 
of  the  stem  that  a  figure  of  it  is  placed  on  exhibition. 
The  portion  preserved  (figs,  i,  2)  was  probably  the 
basal  part  which  was  attached  to  shells,  etc.,  as  seen  in 
fig.  i.  It  was  covered  by  irregular  and  imperforate 
plates  (fig.  2),  which  rested  upon  many  radiating  parti- 
tions, seen  in  fig.  3,  where  the  outer  plates  have  been 
weathered  and  have  disappeared.  They  are  also  seen  in 
fig.  4,  which  is  the  lower  or  attached  side.  There  is  no 
indication  of  arms  or  of  areas  of  plates,  the  ambulacra, 
but  in  the  center  a  stem  is  visible,  which  probably  sup- 
ported the  body.  The  genus  is  chiefly  valuable  in  show- 
ing the  structure  of  a  primitive  stem.  The  five  parts 
making  up  the  column  can  be  distinctly  seen  (fig.  2), 
whereas  in  the  more  specialized  members  of  the  group 
they  are  consolidated  so  that  their  boundaries  cannot  be 
made  out. 

In  the  Cystoid  Amygdalocystis  (PI.  253,  A.  florcahs 
Billings),  the  ambulacra  consist  of  a  double  row  of  imper- 
forate plates  and  are  concealed  by  covering  plates.  This 
double  row  extended  over  the  summit.  The  figure  shows 
several  joints  of  the  ambulacrum,  each  one  of  which  bears 
a  pinnule ;  also  the  body  with  many  plates  indefinitely 
arranged,  and  the  round  stem.  The  mouth  (m)  and  the 
anus  (a)  are  seen  on  the  upper  side. 

In  Mesocystis  (  =  Mesites)  (PI.  254,  M. pusirefski},  the 
five  ambulacra  are  present  and  are  built  on  top  of  the 
body  plates.  While  the  ambulacra  are  imperforate  and 
there  are  no  holes  between  the  plates,  the  body  plates  are 
perforated.  The  position  of  the  ambulacra  in  this  genus 
suggests  their  possible  origin  (see  p.  149).  The  mouth 
(PI.  254,  m)  is  at  the  summit  and  the  anus  (a)  farther 
down  ;  h  is  supposed  to  be  a  hydropore,  though  Lankester 
thinks  it  is  due  to  a  boring  parasite. 


148  SYNOPTIC    COLLECTION. 

We  reach  a  condition  in  Glyptosphaera  (PI.  255,  G. 
leuchtenbergi}  in  which  the  body  plates  are  perforated, 
the  pores  being  in  pairs.  The  ambulacra  are  on  top  of 
the  body  plates,  as  in  Mesocystis.  They  are  long,  nar- 
row, and  branching,  and  are  apparently  without  pores. 
They  lead  to  the  mouth  which  is  covered  by  plates. 

The  body  of  Echinosphaerites  is  globular,  as  shown  by 
PI.  257  (E.  aurantium  Rising);  the  specimen  (No.  256) 
is  somewhat  distorted  by  pressure,  though  with  this 
exception  it  shows  the  characteristic  features  well.  The 
body  is  protected  by  irregular  plates  (No.  256;  PL  257) 
and  provided  with  two  or  three  small  imperfect  arms 
which  are  broken  off  in  most  specimens.  Just  under  a 
thin  limy  film  covering  the  outer  plates  of  the  body  there 
are  ducts  (No.  256),  the  openings  to  which  are  arranged 
in  the  form  of  rhombs,  and  they  are  therefore  called 
"pore-rhombs"  (see  No.  256  and  PI.  257).  These  ducts 
pass  horizontally  from  one  plate  to  the  other,  but  the 
pores  of  the  rhombs  communicate  with  short  canals  that 
pass  vertically  through  the  plates.  Probably  these  canals 
and  pores  aided  in  respiration.  The  mouth  in  Echino- 
sphaerites is  at  the  apex,  while  the  anus  is  on  one  side 
(No.  256)  protected  by  a  pyramid  of  plates,  as  shown  in 
both  specimen  and  figure.  Between  the  mouth  and 
anus,  a  little  to  the  right  of  the  former,  is  the  genital 
pore  (No.  256;  PI.  257). 

One  of  the  more  specialized  Cystoids  is  Caryocrinus 
ornatus  Say  (Nos.  258,  259).  The  stem  by  which  it  was 
fastened  (not  seen  in  the  specimen)  was  composed  of 
many  discs.  Above  the  stem  was  the  body,  protected  by 
circles  of  regular  plates,  finely  seen  in  No.  258.  The 
basal  plates  compose  the  first  circle  and  above  these  is 
the  circle  of  radials  (No.  259).  In  this  genus  the  plates 
at  the  base  of  the  arms,  often  called  interradials,  perform 
the  work  of  true  body  plates.  The  arms  were  perhaps 
little  appendages  like  pinnules,  but  are  usually  broken 
off,  as  in  the  specimens.  The  ambulacra  in  the  middle 


METAZOA  ECHINODERMA.  149 

of  the  arms  were  covered  and  led  to  the  mouth  which  was 
also  covered  over  by  a  series  of  plates.  The  anus  is  in 
the  body  plates  and  outside  of  the  arms.  The  possession 
of  a  complete  digestive  system  ending  in  an  anus  and 
entirely  separate  from  the  body  cavity  is  a  distinctive 
feature  of  the  Echinoderma,  separating  this  subkingdom 
from  the  Coelentera.  The  body  plates  in  Caryocrinus 
were  pierced  by  holes  which  were  the  openings  of  the 
tubes  that  ran  along  the  inner  side  of  the  plates,  and  which 
connected  with  the  respiratory  organs  or  hydrospires. 

In  the  Cystoidea  the  ambulacra  constitute  the  feeding 
and  not  the  locomotive  system,  so  that,  were  we  consider- 
ing function  rather  than  homology,  food  grooves  would  be 
a  good  name  for  ambulacra  and  tentacles  an  appropriate 
name  for  the  organs  which  came  out  of  the  openings  of 
the  food,  grooves.  It  is  probable,  as  we  have  already  said, 
that  the  first  forms  were  without  food  grooves  or  ambula- 
cra ;  these  may  have  appeared  later  as  hollows  scooped 
out  of  the  surface  of  the  body,  so  that  the  ambulacral 
plates  were  set  in  between  the  body  plates.  The  next  step 
might  be  to  set  these  on  top  of  the  body  plates,  as  in  Meso- 
cystis.  Finally,  they  might  be  pushed  upward  still  more, 
until  they  were  off  of  the  body  altogether,  as  in  Caryocri- 
nus, forming  the  ambulacra  of  the  arms. 


BLASTOIDEA. 

The  Blastoids  probably  sprang  from  the  Cystoids.  One 
of  the  most  generalized  Blastoids  is  Codaster  (PI.  260). 
Here  the  body  is  attached  by  a  stem  and  it  is  made  of  reg- 
ular plates  consisting  of  basals,  forked  radials,  and  inter- 
radials.  Its  ventral  side  (PI.  260)  is  wide  and  nearly  flat, 
and  on  this  flattened  area  the  five  imperforate  ambulacra 
(PI.  260,  am)  are  spread  out.  The  many  slits  (PI.  260,  s) 
of  the  hydrospires  are  exposed  between  the  ambulacral 
areas.  The  anus  (PI.  260,  a)  is  flush  with  the  surface. 


150  SYNOPTIC    COLLECTION. 

The  central  mouth  was  concealed  by  oral  plates  in  the 
living  animal,  and  the  ambulacra  were  also  covered.  Co- 
daster  like  all  Blastoids  is  without  arms,  but  short  pinnules 
are  attached  to  the  ambulacra. 

In  another  genus,  Orophocrinus  (PI.  261),  the  numerous 
hydrospiral  slits  are  reduced  to  ten  slits,  two  on  each  side 
of  an  ambulacrum  (PI.  261,  s).  In  this  figure  the  cover- 
ing plates  are  seen  over  the  ambulacra. 

If  we  suppose  the  hydrospires  crowded  under  the  ambu- 
lacral  areas  and  these  slits  shortened  till  only  an  opening 
is  left  at  the  top,  we  have  the  condition  found  in  the  fol- 
lowing more  specialized  Blastoids. 

Pentremites  godoni  Shum.  (No.  262),  is  a  stalked  Blas- 
toid,  but  the  stem  is  so  short  and  small  that  it  is  rarely 
preserved.  The  body  in  this  genus,  as  in  all  Blastoids  of 
its  group  (Pentremitidae),  becomes  constricted  and  the 
inner  portion  of  the  basal  plates  helps  to  form  the  upper- 
most disc  of  the  stem.  The  bas.ils  and  radials  are  well 
seen  in  No.  262,  especially  in  the  middle  specimen  .(b) 
in  the  lower  row,  and  the  upper  right  hand  specimen 
(e).  Each  of  the  five  ambulacra  consists  of  two  parts,  the 
lancet-shaped  portion  in  the  middle  which  is  made  of 
many  small  plates,  and  the  side  pieces  or  plates.  Near 
the  outer  edge  of  the  lancet  plate  there  is  a  row  of  sock- 
ets where  the  long  delicate  pinnules  were  attached.  The 
food  was  caught  by  these  pinnules  and  carried  by  cilia  in 
the  transverse  channels  to  the  median  channel  and  thence 
to  the  mouth  which  was  in  the  center  of  the  oral  disc.  The 
ambulacral  groove  is  said  to  have  been  covered  by  plates, 
but  these  are  not  seen  in  any  of  the  specimens  in  the 
Society's  collection. 

On  the  outer  edges  of  each  ambulacrum  is  a  row  of 
holes  (No.  262,  a,  b,  d,  e)  for  admitting  water  to  the  tubes 
or  hydrospires  inside.  The  latter  open  at  the  top  in  the 
five  holes  or  spiracles  around  the  mouth  (No.  262,  c,  d). 
In  reality  four  of  the  spiracles  are  divided  by  a  partition, 
while  the  largest  one  is  divided  twice.  Of  the  eleven 


METAZOA  —  ECHINODERMA.  151 

openings  thus  formed  ten  are  spiracles  and  one  is  the 
anus. 

We  have  seen  that  the  hydrospiral  or  respiratory 
system  is  not  found  in  the  primitive  forms  of  Cystoids. 
Where  it  first  occurs,  it  is  independent  of  the  feeding 
system  and  is  on  the  surface,  as  in  Echinosphaerites. 
Later,  among  the  Blastoids  especially,  it  is  sunk  under 
and  crowded  closely  against  the  feeding  system. 

Various  interesting  modifications  take  place  in  the 
structure  of  Blastoids.  The  body  may  become  elongated 
and  the  ambulacra  narrow,  as  seen  in  Tricoelocrinus  obli- 
quatus  Worthen  (No.  263),  where  the  lancet  plate  is  cov- 
ered by  the  side  plates. 

In  Nucleocrinus  vernueilli  Troost  (No.  264),  the  basal 
plates  are  very  small  and  sunken;  the  radials  are  also 
reduced  in  size,  while  the  broad  interradials  and  the  nar- 
row ambulacra  make  up  most  of  the  body.  The  latter 
extend  from  the  top  or  ventral  side  downward  to  the 
lower  side. 

One  genus  of  Blastoids,  Eleutherocrinus  (E.  cassedayi 
Shum.,  No.  265),  shows  a  peculiar  specialization  of 
structure.  One  ambulacrum  has  become  modified  and 
is  found  at  the  top,  leaving  only  four  long  ambulacra.  It 
is  interesting  to  note  that  this  specialization  of  the  ambu- 
lacra appears  in  a  stemless  and,  therefore,  a  reduced  blas- 
toid. 

CRINOIDEA. 

The  Crinoidea  may  be  divided  into  two  series,  each 
one  of  which  begins  with  stemmed  species  and  ends  in  a 
stemless  form. 

The  more  generalized  series  is  represented  in  the 
Collection  by  Haplocrinus,  Cupressocrinus,  Cyathocrinus, 
Encrinus,  and  Marsupites. 

Haplocrinus  (No.  266)  has  the  body  made  up  of  two 
circles  of  plates ;  the  circle  at  the  base  of  the  body  and 


152  SYNOPTIC    COLLECTION. 

just  above  the  stem  is  composed  of  basals  and  the  circle 
above  of  radials.  The  other  genera  have  three  circles  of 
plates;  the  one  at  the  base  of  the  body  and  above  the 
stern  is  the  circle  of  underbasals  and  above  this  are  the 
basals  and  radials. 

Those  forms  which  have  basals  and  no  underbasals  are 
known  as  monocyclic  Crinoids  and  those  with  both  basals 
and  underbasals  as  dicyclic  forms. 

According  to  some  investigators  the  monocyclic  Cri- 
noids of  recent  geologic  epochs  and  those  living  to-day 
have  descended  from  the  ancient  dicyclic  forms.  If  this 
is  the  case,  they  have  become  specialized  by  reduction. 
While  this  is  probably  true,  it  must  be  borne  in  mind 
that  the  ancient  dicyclic  forms  may  have  arisen  from  prim- 
itive monocyclic  Crinoids,  which  one  would  expect  to  find 
in  pre-Cambrian  formations. 

According  to  Bather  and  Lankester,1  there  is  evidence 
that  the  monocyclic  forms  have  descended  from  Cambrian 
or  pre-Cambrian  monocyclic  ancestors,  and  the  dicyclic 
species  from  dicyclic  ancestors,  though  it  is  not  known  in 
what  forms  these  two  independent  lines  converge.  We 
will  consider  Haplocrinus  as  an  example  of  the  ancient 
monocyclic  group.  Its  body  (PI.  266,  figs.  1-3,  H.  mespi- 
liformis)  is  small  and  attached  by  a  round  stem  not  seen 
in  the  drawings.  It  is  composed  of  basals  and  radials, 
as  we  have  already  said,  and  these  plates  are  fastened 
together  by  close  sutures,  so  that  they  are  immovable  (fig. 
i,  side  view).  The  radials  are  perforated.  The  ventral 
pyramid  consists  of  oral  plates  only,2  which  rest  upon  the 
radials.  Fig.  2  is  the  ventral  surface  with  the  pyramid  of 
five  oral  plates;  the  posterior  plate  which  contains  the 
anus  is  seen  to  be  larger  and  is  carried  forward  between 
the  lateral-anterior  plates  covering  the  mouth.  Some- 


1  Treat.  Zool.,  Part  III,  1900,  p.  138. 

2  Wachsmuth  and  Springer,  Proc.  Acad.  Nat.  Sci.  Phila.,  1888; 
also  ibid.,  1890. 


METAZOA —  ECHINODERMA.  153 

times  this  tongue-like  projection  has  a  node  on  top,  as  in 
fig.  3.  The  presence  of  the  anus  causes  more  or  less 
irregularity  in  the  plates  of  the  body  (see  fig.  i).  The 
ambulacra  run  out  from  the  mouth  across  the  ventral  disc 
and  under  the  oral  plates  to  the  arms. 

The  arms  in  Haplocrinus  are  only  slightly  developed, 
and  are  usually  broken  off  in  specimens,  but  their  points 
of  attachment  are  seen  (figs.  1-3).  They  consist  of  one 
series  of  sections  divided  by  joints,  and  they  lie  in  grooves 
which  run  along  the  sides  of  the  orals ;  in  two  of  the 
grooves  the  first  section  of  the  arms  is  seen  (fig.  3). 

Haplocrinus  retains  its  simplicity  of  structure  through- 
out life, -remaining  "permanently  in  the  condition  of  a 
very  young  larva."  l 

Certain  peculiar  specializations  of  structure  are  found 
in  Cupressocrinus  abbreviates  Goldf.  (No.  267),  which, 
though  a  primitive  form,  has  developed,  it  would  seem, 
along  a  different  line  from  Haplocrinus. 

This  genus  has  a  stout,  round  stem  (PI.  268,  fig.  2), 
but  according  to  Bather,2  it  "endeavours  at  times  to 
break  with  old  traditions,  and  appears  with  a  triradiate  or 
quinqueradiate  stem  "  (see  PI.  268,  figs.  3,4).  The  body 
is  composed  of  a  centro-dorsal  plate  (fig.  i),  made  of  a 
ring  of  united  underbasal  plates.  Above  this  plate  are 
five  large  basals  and  five  radials  (No.  267;  also  PI.  268, 
figs.  1,2).  In  this  genus  the  regularity  of  the  plates  is 
slightly  disturbed  by  the  anal  plates.  The  ventral  disc  is 
concealed  in  No.  267  by  the  five  short,  simple  arms  which 
are  as  broad  at  their  point  of  attachment  as  the  radial 
plates  (PI.  268,  fig.  i).  These  arms  bore  pinnules  which, 
according  to  Wachsrnuth  and  Springer,  were  arranged  like 
those  of  Blastoids,  there  being  four  or  m ;>re  to  each  arm 
joint.3 

1  Carpenter,  Chall.  Rep.,  Zool.,  XI,  part  32,  1884,  p.  157. 

2  Quart.  Journ.  Geol.  Soc.  London,  Feb.,  1889,  p.  167. 
3Proc.  Acad.  Nat.  Sci.  Phila.,  1886,  p.  180. 


154  SYNOPTIC    COLLECTION. 

The  most  complex  Cyathocrinoid  must  have  passed 
through  a  stage  in  early  life  when  it  closely  resembled 
Haplocrinus.  Cyathocrinus  (PI.  269,  figs,  i-io;  No.  270), 
is  attached  by  a  round  stem  (No.  270,  C.  multibrachiatus 
L.  &  C.;  PI.  269,  fig.  2)  which  never  developed  branches 
or  cirri  (see  figs.  1,4).  Small  underbasal  plates,  five  in 
number,  are  found  (not  seen  in  No.  270,  but  figured  in  PI. 
269,  fig.  i,  young  stage,  and  fig.  3,  plates  of  body  sepa- 
rated). The  underbasals  are  characteristic  of  Palaeozoic 
Crinoids,  as  we  have  already  said,  but  do  not  occur  among 
recent  adult  forms.1  Fig.  4  represents  the  adult  in  which 
the  plates  of  the  body  are  not  so  distinctly  seen  as  in  the 
young  (fig.  i).  Above  the  underbasals  are  five  brasals  and 
five  radials  with  a  small  anal  plate.  These  are  not  seen 
in  No.  270,  but  are  shown  in  figs.  1.3.  The  basals  de- 
velop very  early  in  the  young  and  have  nearly  reached 
their  full  size  when  the  radials  are  still  small.2  An  anal 
tube  (ventral  sac,  Wachsmuth  and  Springer)  rose  from 
the  ventral  surface,  which  was  short  and  covered  by  plates 
(figs,  i,  4,  5). 

The  ambulacral  grooves  run  out  from  the  mouth,  across 
the  ventral  surface,  and  are  concealed  by  small,  irregular 
covering  plates  (fig.  6  ;  fig.  7,  ventral  surface  with  ambu- 
lacrals  and  covering  plates  removed).  When  the  Crinoid 
was  alive,  these  covering  plates  could  open  (fig.  8) ,  and 
thus  food  could  pass  through  the  grooves  (figs.  7,  9)  to 
the  mouth,  after  which  the  covering  plates  were  again 
closed,  as  seen  in  fig.  10. 

A  few  long,  slender  arms  are  sent  off  from  the  radials, 
which  in  some  species  fork  many  times  forming  armlets, 
but  which  are  without  pinnules  (figs.  1,4). 

The  interesting  discovery  was  made  by  Wachsmuth 
and  Springer 3  that  what  had  been  considered  hitherto  as 


i  Chall.  Rep.,  Zool.,  XI,  part  32,  1884,  p.  152. 
2Chall.  Rep.,  loc.  cit.,  p.  169. 

3  Transition  forms  in  Crinoids  and  description  of  five  new  species, 
Proc.  Acad.  Nat.  Sci.  Phila.,  1878,  p.  256. 


METAZOA ECHINODERMA.  155 

four  species l  of  this  genus  were  in  reality  different  stages 
of  growth  of  one  species,  for  which  the  older  name  of 
Cyathocrinus  iowensis  is  retained.  After  an  examination 
of  a  great  number  of  specimens,  it  was  found  that  the 
young  was  represented  by  the  species  C.  divaricatus  Hall 
which  possessed  good-sized  basal  plates.  As  the  animal 
grew  older,  these  plates  became  smaller,  while  at  the  sa/ne 
time  the  radials  (subradials  of  Wachsmuth  and  Springer) 
increased  in  size.  This  is  seen  in  C.  iowensis,  which 
these  authorities  have  proved,  is  identical  with  C.  rimi- 
nalis  Hall.  The  mature  form,  having  the  smallest  basals 
and  largest  radials,  is  C,  malvaceus  Hall. 

Poteriocrinus  zeaeformis  Schultze  (No.  271;  PI.  272, 
figs,  i,  2,  P.  circumtextus  M.  &  G.),  has  a  long  slender 
stem  which  is  not  seen  in  the  figures.  Its  body  is  made 
up  of  underbasal,  basal,  and  radial  plates  with  the  first 
arm  sections  or  brachials  fastened  by  suture  to  the 
radials. 

The  anal  tube  rises  from  the  ventral  disc,  and  is  seen 
in  both  the  specimens  (No.  271)  and  figures  (PI.  272). 
The  long,  delicate  arms  are  forked  and  their  pinnules  can 
be  distinctly  made  out  in  the  specimen  (No.  271). 

Encrinus  liliiformis  Lam.  (No.  273),  is  one  of  the  best 
known  Crinoids.  The  body  is  so  large  that  it  needs 
firmer  support  than  the  stem  alone  can  furnish,  and 
therefore  root-like  extensions  or  cirri  are  thrown  out 
which  help  to  fasten  the  animal  securely  in  the  mud. 
The  plates  of  the  body  are  regular,  consisting  normally  of 
five  underbasals,  covered  by  the  top  stem  joint,  five 
basals,  and  five  radials.  The  oral  plates  are  present  in 
the  young  but  usually  disappear  in  the  adult,  while  the 
anal  plates  are  found  only  in  the  young.  The  anus  per- 
forates the  oral  disc  within  the  circle  of  arms  instead  of 
being  outside  the  arms  as  in  some  Cystoids. 


1  Cyathocrinus  iowensis  O.  &  Sh.,  C.  divaricatus  Hall,   C.  malva- 
ceus Hall,  and  C.  viminalis  Hall. 


156  SYNOPTIC    COLLECTION. 

The  mouth  and  five  ambulacra  are  without  covering 
plates.  The  arms  of  the  very  young  Encrinus  are  at  first 
made  of  single  sections,  that  is,  they  are  uniserial,  but 
afterwards  they  become  biserial1  a  proof  that  the  uni- 
serial condition  is  the  more  primitive. 

In  the  Crinoids  there  were  no  tubes  or  hydrospires,  but 
respiration  took  place  through  pores  between  the  plates 
of  the  oral  surface. 

Marsupites  (No.  274)  is  an  instructive  form.  In  youth 
it  is  attached  by  a  stem,  but  later  it  breaks  away,  and  the 
rounded  posterior  part  of  the  body  usually  shows  no  scar. 
Underbasals,  basals,  and  radials  are  all  present ;  these 
are  thin  and  flexible.2  The  ventral  disc  is  not  preserved 
in  any  of  the  specimens.  The  arms  are  uniserial,  but  are 
usually  broken  off. 

The  second  series  of  Crinoids  is  more  specialized, 
speaking  generally,  than  the  first. 

Platycrinus  (No.  275,  P.  hemisphericus\  PI.  276,  P.  tri- 
gintidactylus  Aus.)  has  a  body  made  of  basals  and  radinls, 
the  former  of  which  are  unequal.  From  the  ventral  side 
rises  a  large  anal  tube  (see  PI.  276).  The  arms  are  free, 
they  fork  a  few  times,  and  are  well  supplied  with  pinnules. 
The  ambulacra  are  concealed  by  covering  plates. 

Actinocrinus  (No.  277)  has  a  small  body  without 
underbasals,  and  the  arms  are  attached  near  its  middle. 
The  basals  are  reduced  to  three  in  this  genus.  The 
specimen  (No.  277  a)  has  eight  arms,  and  the  pinnules 
of  one  are  fairly  well  preserved.  The  food  was  caught 
by  the  pinnules  and  carried  down  to  the  base  of  the  arms 
where  it  passed  through  the  covered  tunnels  of  the  ambu- 
lacra to  the  mouth.  The  convergence  of  these  ambula- 
cral  grooves  a  little  to  one  side  of  the  center  is  seen  in 
the  internal  casts  of  Actinocrinus  (No.  277  b-d) .  Here 

1  Wachsmuth  and  Springer,  Proc.  Acad.  Nat.  Sci.  Phila.,  1886,  p. 
230. 

2  Bather,  Proc.  Zool.  Soc.  London,  1895,  p.  996. 


METAZOA  —  ECHINODERMA.  157 

the  grooves  have  become  filled  with  solid  matter,  but  the 
position  of  the  parts  is  well  shown.  The  branching  of 
the  arms  on  leaving  the  body  is  seen  in  another  cast,  No. 
277  e,  where  the  aboral  side  is  uppermost. 

From  the  oral  disc  extended  a  long  anal  tube.  This 
is  seen  in  No.  277  a,  while  its  position  is  indicated  in  the 
casts.  Respiration  was  probably  effected  in  Actinocrinus 
by  tentacles  on  the  edges  of  the  ambulacra. 

Marsupiocrinus  (No.  278,  M.  caelatus  Phil.)  has  a  lower 
oral  vault  than  Actinocrinus,  and  it  is  composed  of  a  larger 
number  of  plates  than  usually  is  found.  The  arms  are 
provided  with  pinnules  (No.  278)  but  are  unbranched. 
Similar  in  general  structure  to  Marsupiocrinus  is  Eucalyp- 
tocrinus  caelatus  Hall  (No.  279).  This  Crinoid  when  full 
grown  had  a  large,  plump,  complex  body,  which  was  con- 
cave at  the  bottom,  the  basals  and  in  some  cases  the  radi- 
als  extending  upward  and  forming  a  cone.  The  arms  are 
comparatively  small,  set  in  deep  recesses  (No.  279),  and 
the  ambulacra  have  the  same  structure  as  in  Actinocrinus. 
Here  the  anal  tube  was  very  long  and  large. 

Apiocrinus  (No.  280)  differs  from  the  preceding  in  that 
the  stem  forms  a  portion  of  the  body.  These  two  parts 
can  always  be  distinguished  from  each  other,  as  the  por- 
tion corresponding  to  the  body  of  other  Crinoids  has 
vertical  and  oblique  lines,  while  the  stem  portion  has  only 
circular  lines,  dividing  it  into  horizontal  discs.  The 
ambulacra  are  uncovered,  and  there  is  no  vault  or  anal 
tube. 

Millericrinus  mespiliformis  d  'Orb.  (No.  281),  is  similar 
to  Apiocrinus  in  some  respects.  As  a  general  thing  both 
have  the  stem  enlarged,  but  that  of  Millericrinus  widens 
more  gradually,  and  the  upper  joint  is  not  much  larger 
than  those  below  it.  Recently,  vestiges  of  underbasals 
have  been  found  in  two  species  of  this  genus,  and  in  both 
cases  these  plates  had  separated  from  the  basal  and  be- 
come attached  to  the  top  stem  joint  (No.  281). 

Most  of  the  forms  of  Crinoids  already  described  have 


158  SYNOPTIC    COLLECTION. 

had  a  body  composed  of  five  basals  and  five  radials. 
This,  however,  is  not  the  case  with  Trigonocrinus.  Its 
peculiar  structure  tends  to  prove  that  it  is  a  form  special- 
ized by  reduction.  PL  282,  figs.  1-5,  illustrate  the  prob- 
able evolution  of  this  genus.  Starting  as  a  normal  Crinoid 
with  five  basals  and  five  radials  (fig.  i)  it  loses  in  time 
one  basal  and  one  radial  and  is  like  fig.  2.  Three  basals 
then  become  larger  at  the  expense  of  one,  while  two 
radials  increase  in  size  (fig.  3).  Trigonocrinus  has 
reached  the  stage  represented  by  fig.  4,  in  which  the  three 
basals  are  fused  into  one  ring  with  only  a  vestige  of  the 
fourth  plate,  while  two  of  the  radials  are  usually  fused. 
If  this  process  of  specialization  by  reduction  is  carried 
still  farther,  the  vestige  of  a  fourth  basal  would  disappear 
and  the  two  radial  plates  would  become  united,  leaving 
no  suture,  so  that  one  could  see  only  three  basals  and 
three  radials  (fig.  5). 

An  illustration  of  a  Crinoid  specialized  by  reduction  is 
found  in  Cheirocrinus  (No.  283,  model  of  C.  r&rttrHaH). 
For  some  reason  the  body  with  its  drooping  arms  hung 
downward  from  the  top  of  the  stem  (No.  283).  This 
peculiar  and  unfavorable  position  has  doubtless  caused 
the  irregularity  in  the  body  plates,  and  a  reduction  in  the 
number  of  basals  from  five  to  three.  The  radials  vary  in 
form  and  bear  only  three  arms. 

The  living  Crinoids  are  represented  in  this  Collection 
by  Metacrinus,  Pentacrinus,  Antedon,  and  Thauma- 
tocrinus. 

The  magnificent  specimen  of  the  living  Crinoid,  Meta- 
crinus interruptus  Carp.  (No.  284),  shows  some  of  the  parts 
on  a  large  scale.  The  long  stem  is  nearly  round  at  its 
base,  though  it  becomes  pentagonal  higher  up.  Many 
jointed  cirri  are  given  off  in  whorls  along  the  whole  length 
of  the  stem  and  the  latter  are  closer  together  near  the 
body.  The  body  itself  is  surprisingly  small.  It  consists 
of  little  basal  and  radial  plates,  while  the  lower  plates  of 
the  five  arms  help  to  make  up  a  portion  of  its  upper  part. 


METAZOA ECHINODERMA.  1 59 

The  large  branching  arms  with  their  many  pinnules  are 
extremely  graceful  organs.  The  disc  is  small  and  the 
ambulacra  extend  from  the  mouth  to  the  ends  of  the  arms. 

The  body  is  also  small  in  Pentacrinus  (No.  285),  con- 
sisting chiefly  of  five  basals  and  five  radials.  There  are 
vestiges  of  underbasals,  but  these  are  sometimes  wholly 
resorbed  in  the  adult.  Pentacrinus  is  attached  by  a  long 
pentagonal  stem  (No.  286),  the  joints  of  which  bear  cirri. 
The  ventral  surface  is  flexible  and  has  many  irregular 
plates.  The  mouth  is  exposed  and  from  it  extend  the  five 
uncovered  ambulacra. 

The  uniserial  arms  are  greatly  developed,  having  a 
large  number  of  branches  which  are  well  supplied  with 
pinnules. 

Antedon  (  =  Comatuld)  rosacea  Linck  (PL  287  ;  No.  288) 
is  a  living  Crinoid  of  great  interest,  inasmuch  as  its  devel- 
opment recapitulates  in  a  marked  degree  the  history  of 
the  group  to  which  it  belongs. 

After  escaping  from  the  egg,  the  embryo  is  free  and 
moves  by  means  of  bands  of  cilia  (PI.  287,  fig.  i).  Early 
on  the  eighth  day  (Bury)  after  development  began,  the 
larva  became  attached.  On  the  tenth  day  the  larva  had 
developed  a  stem  (fig.  2).  In  this  stage  the  underbasals 
are  found  (fig.  2.  ub}  and  above  these  the  basals  (fig.  2, 
b) .  Although  the  sutures  indicate  only  three  under- 
basal  plates,  one  small  and  two  large,  nevertheless  it  is 
probable  that  each  large  plate  is  formed  by  the  coales- 
cence of  two  plates,  so  that  originally  there  were  five 
underbasals.1 

The  resemblance  of  Antedon  to  a  Cystoid  is  now  strik- 
ing, and  the  existence  of  underbasals  in  the  young  is  evi- 
dence of  descent  from  the  Palaeozoic  Crinoids  in  which 
we  have  already  seen  underbasals  well  developed.  As 
Antedon  grows  older,  the  underbasals  and  the  top  stem 
joint  fuse  into  a  single  plate,  the  centro-dorsal,  so  that 

'Phil.  Trans.  Roy.  Soc.  London,  CLXXIX,  1888,  p.  288. 


160  SYNOPTIC    COLLECTION. 

Antedon  passes  through  the  condition  already  shown  by 
Millericrinus  (No.  281). 

The  armless  Cystoid  stage  passes  into  the  Penta- 
crinoid  stage,  in  which  uniserial  arms  grow  out  (fig.  3). 
These  continue  to  increase  in  number.  The  centro-dorsal 
plate  develops  cirri,  and  by  this  time  all  trace  of  the 
underbasals  is  lost.1 

When  ten  cirri  are  developed,  a  separation  takes  place 
between  the  centro-dorsal  plate  and  the  stem ;  the  latter 
is  left  attached,  while  the  animal  breaks  away  and  is 
henceforth  free. 

A  tiny  opening  is  left  in  the  middle  of  the  aboral  side, 
but  later  this  is  filled,  though  traces  of  the  scar  may  be 
seen  internally. 

After  the  animal  liberates  itself  from  its  stem,  it  swims 
freely  in  the  water.  The  cirri  are  used  occasionally  for 
crawling  about  on  marine  plants,  or  at  other  times  for 
anchoring  itself  to  rocks.  According  to  Carpenter,  2  the 
adult  Antedon  has  the  habit  of  fixing  itself  to  a  rock  and 
remaining  for  long  periods.  In  this  stage  the  body  is 
extremely  small  and  the  basals  have  become  metamor- 
phosed into  the  so  called  rosette,  which  is  wholly  con- 
cealed in  the  cavity  of  the  ring  formed  by  the  radials. 

The  mouth  is  in  the  middle  of  the  oral  disc  and  at  one 
side  of  this  opening  is  the  anal  tube.  The  fiye  arms 
divide  almost  immediately  to  form  ten  organs  which  are 
disproportionately  large  for  the  size  of  the  body  and  are 
well  provided  with  pinnules. 

The  floor  of  each  ambulacral  groove  is  ciliated,  and  the 
five  ciliated  grooves  extend  from  the  mouth  over  the  oral 
disc  to  the  ends  of  the  arms. 

Actinometra  (No.  289)  is  similar  to  Antedon  but  differs 
from  it  by  having  the  mouth  at  one  side  of  the  oral  disc 
and  the  anal  tube  near  the  center. 


1  Carpenter,  stated   by  Wachsmuth    and   Springer,  Proc.  Acad. 
Nat.  Sci.  Phila.,  1888,  p.  352. 

2  Phil.  Trans.  Roy.  Soc.  London,  CLVI,  1866,  p.  698. 


METAZOA ECHINODERMA.  161 

ASTEROIDEA. 

It  is  probable  that  Agelacrinus,  belonging  to  the  Agel 
acrinidae,  was  a  descendant  of  an  ancestral  form  from 
which  the  Asteroidea  or  starfishes  of  to-day  arose.  Using 
a  simple  but  clear  illustration  we  may  say  that  if  the 
hand  should  represent  this  trunk  form,  then  the  first  fin- 
ger would  stand  for  the  Agelacrinidae.  Another  finger 
would  represent  the  Asteroidea  which  began  with  the 
same  trunk  but  developed  along  another  and  quite  inde- 
pendent line. 

Since  Agelacrinus  comes  nearer  the  probable  ancestral 
form  than  any  other  fossil  or  any  living  species,  we  begin 
the  study  of  the  Asteroidea  with  this  genus.  Agelacrinus 
(No.  290,  A.  rhenanus}  was  without  a  stem,  but  it  was 
attached  by  its  dorsal  or  aboral  side.  The  circular  flat- 
tened .  body  was  covered  by  a  great  number  of  small 
irregular  plates  which  were  imbricated  or  arranged  like 
shingles  on  a  roof.  These  plates  were  perforated,  and 
usually  the  pores  were  in  pairs.  The  mouth  was  in  the 
middle  of  the  upper  side  and  was  covered  by  plates. 
Radiating  from  the  mouth  were  five  ambulacra  (No.  290) 
also  protected  by  covering  plates.  At  the  tip  of  each 
ambulacrum  there  was  a  hole  for  the  admission  of  water. 
Each  ambulacrum  consisted  of  two  rows  of  plates  and 
between  these  plates  there  were  holes. 

The  anus  was  situated  in  one  of  the  areas  outside  of 
the  oral  disc,  and  between  two  of  the  ambulacra  ;  it  was 
also  covered  by  plates  which  were  set  into  the  body 
plates. 

The  irregularity  of  the  body  plates,  the  absence  of- 
arms,  and  the  fact  that  the  mouth,  ambulacra,  and  anus 
were  concealed  by  plates,  all  remind  one  of  both-  the 
Cystoids  and  the  Blastoids.  Zittel  places  this  genus  with 
the  Cystoidea,  though  it  seems  to  have  more  points  of 
resemblance  with  the  Asteroidea. 


162  SYNOPTIC    COLLECTION. 

Since  specialized  Asteroidea  occur  with  the  Cystoidea 
in  the  Cambrian  formations,  it  is  impossible  for  the 
former  to  have  descended  from  the  latter.  We  must, 
therefore,  look  for  the  ancestors  of  both  groups  in  the 
pre-Cambrian  rocks,  and  it  seems  most  likely  that  such 
a  form  will  combine  the  characters  of  both  Cystoidea  and 
Asteroidea.  Most  of  the  Palaeozoic  starfishes,  like  those 
of  to-day,  were  free -moving  and  crawled  with  the  oral  or 
actinal  side  downward.  If  we  suppose  an  ancient  star- 
fish to  be  attached  by  a  stem  extending  downward  from 
the  middle  of  the  aboral  or  abactinal  surface,  we  have 
a  striking  resemblance  to  a  stalked  Crinoid.  In  such  a 
case  the  mouth  is  in  the  middle  of  the  upper  side  and 
the  ambulacra  run  out  from  it  into  the  arms.  When, 
however,  the  starfish  became  free-moving,  it  turned  upon 
the  ventral  side  and  the  tentacles  which  had  been  use- 
ful in  catching  food  became  modified  in  time  into  loco- 
motor  organs. 

It  seems  probable  that  the  ancestral  starfishes  had  a 
pentagonal  body  with  spines  slightly  developed,  and  two 
rows  of  plates  in  each  ambulacrum,  the  plates  of  one 
row  alternating  with  those  of  the  other.  One  of  the 
descendants  of  such  a  form  may  be  the  living  Ctenodiscus 
(No.  291,  C.  crispalus  D.  £  Kor.).  When  young  (No. 
291  a),  it  has  a  dome-like  body  which  becomes  flatter  with 
age  (No.  291  b,  c).  The  adult  has  a  large  disc  and  short 
arms,  giving  it  a  pentagonal  outline.  The  plates  of  the 
aboral  side  (No.  291  b)  are  small  and  leathery,  the  spines 
being  slightly  developed.  Near  the  center  is  the  anal 
tubercle.  Each  ambulacrum  on  the  ventral  side  (No. 
291  c)  consists  of  two  rows  of  alternating  plates  which 
are  broad  and  not  crowded  closely  together.  There  are 
two  rows  of  holes  for  the  tentacles  which  are  without 
sucking  discs.  Every  ambulacrum  is  flanked  on  each 
side  by  a  row  of  good-sized  interambulacral  plates,  and 
outside  of  these  are  well  developed  marginal  plates  (No. 
291  c). 


METAZOA ECHINODERMA.  168 

Gradually  the  pentagonal  form  tended  to  give  way  in 
Palaeozoic  time  to  the  stellate  form  illustrated  by  the 
ancient  starfish  Palaeaster  (No.  292,  model).  The  plates 
of  the  aboral  side  of  the  central  disc  are  small  and  indefi- 
nite, but  those  of  the  arms  are  more  or  less  regular 
(No.  292,  specimen  on  the  left).  The  anus  is  found  on 
the  aboral  side,  though  the  model  does  not  show  its  posi- 
tion. The  mouth  is  uncovered,  but  is  surrounded  by 
five  plates.  The  ambulacra  are  also  uncovered  and  con- 
sist of  two  rows  of  alternating  plates  (No.  292,  specimen 
on  the  right)  ;  on  the  outer  edge  of  each  plate  there  is  an 
opening  for  a  tentacle  (No.  292).  Thus  there  are  two 
straight  rows  of  holes  extending  through  each  ambulacral 
groove. 

On  either  side  of  the  ambulacral  plates  there  is  a 
row  of  prominent  interambulacral  (adambulacral,  Zittel) 
plates  (No.  292  b),  and  outside  of  these  are  large  margi- 
nal plates. 

Respiration  was  effected  in  these  early  forms  as  in 
modern  species  by  means  of  a  water  system  consisting  of 
a  sieve  or  madreporic  body,  which  in  ancient  forms  was 
on  the  ventral  side  (Zittel),  and  of  radiating  tubes. 

The  primitive  forms  are  also  represented  by  A stropecten 
variabilis  Liitk.  (No.  293),  in  which  the  marginal  plates 
are  conspicuous.  Here  the  arms  are  more  tapering  than 
in  Ctenodiscus,  but  the  tentacles  are  still  pointed  and 
remain  in  two  rows. 

In  Hippasteria  phrygiana  Ag.  (No.  294),  the  ambu- 
lacral plates  are  opposite  and  not  alternating  ;  the  tenta- 
cles are  in  two  rows,  but  instead  of  being  pointed  they 
are  provided  with  sucking  discs  and  are,  therefore,  no 
longer  true  tentacles  but  rather  locomotive  organs  or 
"  tube  feet."  These  organs  are  seen  in  the  preparation 
(No.  295)  which  is  a  dissection  to  show  the  water-vascu- 
lar system  after  injection  with  blue  coloring  fluid.  This 
system  will  be  described  more  at  length  under  the  com- 
mon starfish,  Asterias  (see  pp.  165-169).  The  ovaries 


164  SYNOPTIC    COLLECTION. 

and  their  openings  are  also  seen  in  this  preparation.  No. 
296  shows  the  stomach  and  its  coecal  appendages. 

The  marginal  plates  in  these  forms  are  large,  but  those 
on  the  upper  side  have  become  small  in  Pentaceros 
modestus  Gray  (No.  297).  The  interambulacral  plates  are 
of  good  size  and  the  tube  feet  have  large  suckers.  The 
aboral  disc  and  the  sides  of  the  arms  are  provided  with 
stout  conical  spines. 

This  tendency  for  the  large  marginal  plates  of  the 
primitive  forms  to  become  reduced  in  size  is  seen  in 
Paulia  horrida  Gray  (No.  298).  The  spines  in  this 
genus  are  large  and  strong,  and  are  found  on  the  most 
exposed  points. 

In  the  starfishes  so  far  described  the  development  of 
the  ambulacral  system  and  of  the  test  or  skeleton  goes 
on  together,  but  in  the  more  specialized  forms  which 
follow,  the  development  of  the  ambulacral  system  is 
accelerated.1 

In  Linckia  unifascialis  Gray  (No.  299)  the  disc  is 
small  and  the  arms  long  and  six  in  number.  Like  the 
earlier  forms  it  is  spineless.  The  marginal  plates  are 
reduced  in  size.  The  ambulacra  are  narrow  and  some- 
what crowded,  while  they  carry  two  rows  of  tube  feet 
provided  with  suckers.  The  tendency  to  multiply  the 
number  of  arms  is  seen  in  Solaster  endeca  Forbes  (No. 
300).  Here  there  are  nine  rays  radiating  from  a  disc  of 
considerable  size.  There  are  few  spines,  and  the  surface 
is  granular.  The  two  rows  of  ambulacral  feet  are  pro- 
vided with  sucking  discs. 

The  deep-sea  species,  Zoroaster  fulgens  Wyv.  Thorn. 
(PI.  301,  figs.  1-3),  is  of  especial  interest.  The  young 
(fig.  i)  has  a  much  higher  disc  than  the  adult.  The 
plates  of  the  aboral  side  are  distinctly  seen,  and  for  this 
reason  the  genus  is  an  admirable  one  for  comparison 
with  Crinoids.  The  central  plate  is  surrounded  by  five 

1  Sladen,  Chall.  Rep.,  Zool.,  XXX,  part  51,  1889,  p.  xxxv. 


METAZOA ECHINODERMA.  165 

small  underbasals  (fig.  i)  and  five  basals  (shaded  in 
fig.  i).  Outside  of  these  are  five  radials.  Regular 
plates  extend  outward  to  t-he  tip  of  the  arms,  where  are 
found  the  terminal  or  ocular  plates.  This  definite  ar- 
rangement of  plates  so  finely  illustrated  by  both  the 
larval  and  adult  Zoroaster,  occurs  in  some  of  the  larvae 
of  the  more  specialized  Asteroidea,  but  is  soon  lost  in, the 
process  of  development. 

While  these  characters  are  all  of  a  primitive  nature, 
Zoroaster  possesses  other  peculiarities  which  place  it 
near  the  more  specialized  genus  Asterias.  The  disc  is 
small  and  the  arms  long  and  tapering  (fig.  2,  showing 
spines  but  not  plates).  The  tube  feet  have  sucking  discs, 
and,  unlike  the  genera  already  described,  there  are  four 
rows  of  these  locomotive  organs  (fig.  3). 

One  of  the  commonest  starfishes  on  the  New  England 
coast  is  Asterias  forbesi  Verr.  (Nos.  302-308).  This  ani- 
mal passes  through  an  indirect  development  with  a 
marked  and  peculiar  metamorphosis. 

Like  most  starfishes  when  young,  the  larva  or  brachio- 
laria,  as  it  is  called,  is  bilateral  with  four  arms  on  either 
side,  so  that  the  marked  radial  symmetry  which  appears 
later  is  a  secondary  and  not  a  primitive  character. 

The  aboral  side  is  raised  and  more  or  less  dome- 
shaped.  The  spines  are  in  regular  rows,  according  to  A. 
Agassiz,  and  the  plates  remind  one  of  those  of  Crinoids. 
Underbasal  plates  have  been  found  in  two  species  of 
Asterias  (A.  rtibens  and  A,  glarialis1).  The  basals  and 
radials  appear  in  the  very  young  larva  and  are  homolo- 
gous with  the  same  plates  in  the  Crinoid ;  but  as  develop- 
ment goes  on,  it  becomes  impossible  to  trace  them.  By 
many  authors  the  terminals  or  ocular  plates  of  starfishes, 
Ophiurans,  and  sea  urchins  have  been  considered  as 
homologous  with  the  radials  of  Crinoids ;  but  it  has  been 
shown2  that  the  radials  in  starfishes  are  developed  be- 

'Sladen,  Quart.  Journ.  Micr.  Sci.,  XXIV,  1884,  p.  34. 
2  Sladen,  ibid.,  p.  29. 


166  SYNOPTIC    COLLECTION. 

tween  the  basals  and  terminals,  and  that  the  latter  are 
pushed  outward  with  the  growing  arms.  These  are  addi- 
tional plates  and  are  not  horaologous  with  any  plates  of 
the  Crinoids.  The  anus  in  the  young  is  near  the  edge  of 
the  oral  or  actinal  side. 

The  arms  at  this  time  are  broad,  short,  and  unequal  in 
length.  The  ambulacra  running  out  from  the  mouth  have 
two  rows  of  organs  which  are  like  tentacles,  being  pointed 
at  the  end.  The  madreporic  body  is  near  the  edge  of 
the  actinal  side.  As  the  starfish  grows  older,  radial 
symmetry  predominates,  and  the  five  equal  arms  radiate 
from  the  small  central  disc.  The  body  becomes  flat- 
tened, and  the  spines  and  plates  more  or  less  irregular. 
The  monotony  of  the  spiny  upper  surface  is  broken  by 
the  little  radiately-grooved  madreporic  body  (No.  302) 
which  has  moved  from  the  actinal  area  and  is  at  the  junc- 
tion of  two  arms  on  the  abactinal  side.  The  anus  has  also 
moved  and  is  near  the  center  of  the  abactinal  side.  The 
ambulacra  carry  four  rows  of  organs  which  have  devel- 
oped suckers  at  the  ends  and  become  thereby  efficient 
locomotive  organs. 

In  the  center  of  the  ventral  side  is  the  mouth  sur- 
rounded by  a  membrane  and  guarded  by  five  sets  of 
spines. 

Although  the  normal  number  of  arms  is  five,  it  some- 
times happens  that  only  four  are  developed.  On  the 
other  hand  in  a  collection  of  about  eight  hundred  star- 
fishes from  Salem  Harbor,  there  were,  according  to  Mr. 
N.  L.  Wilson,  two  six-rayed  specimens  and  one  seven- 
rayed  specimen. 

The  power  of  the  animal  to  reproduce  lost  arms  is 
shown  in  No.  303  where  four  arms  have  been  lost,  but 
one  has  grown  out  to  half  the  size  of  the  fully  grown 
arms.  No.  304  is  probably  a  starfish  that  has  been 
wounded  in  some  way.  In  trying  to  repair  the  injury  it 
produced  the  semblance  of  an  arm.  A  specimen  of  this 
kind  is  met  with  occasionally  on  our  coast. 


METAZOA ECHINODERMA.  167 

The  skeleton  of  the  adult  is  composed  of  an  irregular 
network  of  beams  and  spines  which  are  covered  by  a  thin 
layer  often  called  the  epidermis.  This  layer  can  be 
scraped  off  with  a  knife,  proving  that  the  skeleton  is 
internal.  The  majority  of  the  spines  are  immovably  fast- 
ened to  the  beams  of  the  skeleton,  but  on  the  lower  side 
along  each  ambulacrum  there  are  spines  of  quite  a  differ- 
ent character  from  those  above.  These  are  more  slender 
and  tapering,  and  are  connected  with  the  skeleton  either 
by  cushions  or  by  ball-and-socket  joints,  allowing  of  con- 
siderable freedom  of  motion.  Among  the  spines  of  the 
starfish  are  little  characteristic  forked  organs  called  pedi- 
cellariae,  which  are  spines  modified  for  a  special  purpose 
not  yet  known  with  certainty,  though  it  is  evident  that 
they  are  used  for  taking  hold  of  objects.  They  are  found 
at  the  bases  of  the  spines,  on  the  soft  membrane  between 
the  spines,  and  also  on  the  movable  spines  of  the  lower 
side.  In  those  Asteroidea  that  have  four  rows  of  tube 
feet  there  are  two  kinds  of  pedicellariae ;  in  one  the 
blades  are  opposite  and  in  the  other  they  cross  like  scis- 
sors. 

The  plates  of  the  skeleton  are  finely  seen  in  the  prepara- 
tion. No.  305  (specimen  on  the  left)  shows  the  irregular 
network  of  plates  in  the  upper  side  or  back,  and  the  speci- 
men on  the  right  the  two  rows  of  ambulacral  and  interam- 
bulacral  plates  in  the  lower  side.  The  ambulacral  plates 
are  movably  articulated  at  the  inner  end.  Between  the  am- 
bulacral plates  can  be  seen  the  four  rows  of  holeb  through 
which  pass  the  tube  feet  with  sucking  discs  at  their  ends. 
On  each  side  of  the  groove  formed  by  the  ambulacral 
plates  is  the  row  of  rounded,  imperforate  interambulacral 
plates  which  bear  the  movable  spines  already  described. 
Nos.  306-308  are  preparations  of  the  starfish,  showing  the 
internal  structure.  The  mouth  leads  into  a  stomach  which 
can  be  thrown  over  a  mussel  or  other  animal.  By  the 
power  of  suction  the  food  is  taken  in  and  the  hard  parts 
thrown  out  of  the  mouth.  A  coecal  prolongation  is  con- 


168  SYNOPTIC    COLLECTION. 

tinued  from  the  stomach  into  each  arm  (No.  306).  The 
stomach  is  extended  above  into  a  short,  indefinite  intestine 
which  opens  near  the  center  of  the  aboral  area.  It  does 
not  seem  to  be  functionally  useful  and  may  be  the  remain- 
ing vestige  of  the  well  defined  anus  of  the  Crinoids  (Pack- 
ard). Opening  into  the  intestine  is  the  liver  which  consists 
of  two  long  branches  that  extend  into  each  arm  (see  No. 
306).  According  to  Griffith  and  Johnstone1  the  "saccu- 
lar  diverticula  "  of  the  starfish  are  not  hepatic  but  pancre- 
atic in  function.  On  chemical  analysis  they  find  the  secre- 
tion is  similar  to  that  of  the  vertebrate  pancreas. 

The  reproductive  organs  —  ovaries  or  testes  —  are  on 
either  side  of  each  arm  (No.  308)  and  open  by  slits  at 
the  base  of  the  arms  near  their  junction  with  the  central 
disc. 

No.  306  and  also  No.  307  are  specimens  injected  with 
blue  colored  fluid  to  show  the  water-vascular  system, 
which  arises  as  an  outgrowth  from  the  digestive  system 
as  is  the  case  with  the  Ctenophora.  It  consists  of  the 
madreporic  body,  a  short  canal  called  the  stone  canal 
which  extends  to  a  circular  ring  around  the  mouth  (cir- 
cumoral  ring)  from  which  five  radial  vessels  are  given  off, 
one  into  each  arm  ;  these  in  turn  connect  with  the  water 
sacs  or  ampullae  of  the  tube  feet  which  are  seen  in  No. 
307  extending  in  rows  to  the  tip  of  each  arm.  The  true 
vascular  blood  system  is  difficult  to  observe.  The  heart 
or  pulsating  vessel  runs  parallel  with  the  stone  canal. 
The  body  cavity  is  filled  with  a  watery  fluid  containing 
corpuscles  evidently  representing  the  blood  of  more  spe- 
cialized animals.  There  are  also  delicate,  tubular  organs, 
described  as  dermal  branchiae,  extending  from  the  dorsal 
surface,  which  probably  have  a  respiratory  function; 
sometimes  these  may  be  seen  swollen  with  water.  On 
the  dorsal  side  there  are  many  minute  pores  through 
which  water  may  enter  or  leave  the  body  cavity. 

1  Proc.  Roy.  Soc.   Edinburgh,  XV,  1888  ;  quoted  in  Amer.  Nat., 
XXIII,  1889,  p.  1101. 


METAZOA  —  ECHINODERMA.  169 

The  preparation  (No.  308)  shows  the  nervous  system 
in  part.  This  consists  of  a  ring  encircling  the  esopha- 
gus, and  radial  nerves  which  are  the  white  cords  seen  in 
No.  308  running  to  the  end  of  the  arms. 


OPHIUROIDEA. 

The  evidence  seems  to  point  to  the  view  that  the  Ophiu- 
rans  have  descended  from  some  one  of  the  more  specialized 
Crinoids  -1  Notwithstanding  that  many  genera  retain 
throughout  life  the  underbasals,  basals,  and  radials  of  the 
abactinal  area  possessed  by  some  Crinoids  and  by  larval 
Asteroidea,  nevertheless  peculiar  modifications  have  arisen 
which  place  the  adult  Ophiurans  farther  from  the  primi- 
tive, pentagonal,  larval  form  than  the  adult  Asteroids. 

Generally  speaking  the  radials  are  developed  before  the 
basals  and  underbasals,  and  are  of  large  size.  We  have 
seen  in  the  specialized  Crinoids  the  tendency  toward  the 
increasing  development  of  the  radials  and  the  reduction 
of  the  basals. 

It  has  been  shown  by  Fewkes2and  others  that  the 
young  Ophiuran,  like  Asterias,  is  at  first  bilaterally  sym- 
metrical and  that  later  it  takes  on  the  pentagonal  form 
which  gradually,  with  the  development  of  the  arms, 
changes  to  the  modified  stellate  condition  of  the  adult. 
The  bilateral  larva  possesses  an  intestine  and  anus,  but 
later  both  disappear,  so  that  the  adult  is  more  reduced  in 
this  particular  than  the  starfish. 

Ophiopholis  aculeata  Gray  (No.  309),  has  a  circular, 
sharply  defined  disc  which  bears  minute  spines.  The  longr 
rounded,  un branched  arms  run  out  directly  from  the  disc 
and  are  of  about  the  same  size  throughout.  They  are  pro- 
tected by  haj-d  plates, —  dorsal,  lateral,  and  ventral  shields,. 

1  Sladen,  Quart.  Journ.  Micr.  Sci.,  XXIV,  1884. 

2  Bull.  Mus.  Comp.  Zool.,  XIII,  no.  4,  1887,  p.  107. 


170  SYNOPTIC    COLLECTION. 

—  the  homologies  of  which  are  a  subject  of  much  discus- 
sion. 

It  is  generally  considered  that  the  ambulacral  plates  are 
inside  the  arms  in  the  form  of  an  axis  of  jointed  sections 
or  arm-bones.  If  this  is  the  case,  then  the  ventral  plates 
are  additional  ones  and  are  not  homologous  with  any  other 
plates  of  the  Asteroids.1  They  may  be  developed  for  the 
purpose  of  protecting  the  delicate  water-tube,  blood-tube, 
and  nerves  which  run  through  the  arms  and  which  are  ex- 
posed in  Asterias.  The  lateral  plates  bear  lateral  spines 
which  are  probably  helpful  in  locomotion.  Each  arm-bone 
is  pierced  by  a  water-tube  or  tube  foot  which  is  without 
ampulla  or  sucking  disc,  and  therefore  of  no  use  as  a  lo- 
comotive organ.  These  tube  feet  come  out  between  the 
ventral  and  lateral  shields.  Above,  the  base  of  each  arm 
is  protected  on  either  side  by  the  so  called  radial  shields, 
while  below  near  the  mouth  are  the  oral  shields. 

The  internal  organs  are  all  concentrated  within  the  disc. 
The  genital  organs  open  by  slits  on  the  lower  side  at  the 
base  of  the  arms.  The  madreporic  body  is  also  on  the 
lower  side  in  one  of  the  mouth  plates.  Ophiopholis  de- 
velops without  a  metamorphosis.  The  disc  of  Ophiura 
(No.  3'io,  O.  panamteri  Liitk.)  is  granulated,  and  the 
arms  are  well  protected  by  the  numerous  short  flattened 
spines. 

Ophioplocus  (No.  311)  resembles  Ophiura  in  having  a 
granulated  disc.  The  radial  shields  are  small.  Ophio- 
coma  cethiops  Liitk.  (No.  312)  has  wide  upper  arm-plates 
and  large  spines. 

The  young  Astrophyton  resembles  the  typical  Ophiuran 
in  having  a  flat  disc  covered  by  plates.  In  the  process 
of  growth,  these  become  covered  by  a  granulation  and 
later  both  granulation  and  plates,  except  those  at  the  mar- 
gin, disappear.2 

1  Bull.  Mus.  Comp.  Zool.,  loc.  cit.,  p.  144. 
2Chall.  Rep.,  Zool.,  V,  part  14,  1882,  p.  253. 


METAZOA ECHINODERMA.  171 

The  radial  shields  increase  in  size.  The  arms  divide 
many  times  and  the  great  number  of  flexible  branches 
intertwine  with  one  another,  giving  a  basket-like  appear- 
ance, and  the  name  of  Basket-fish,  to  the  animal  (No.  313). 
These  arms  are  without  the  dorsal  or  ventral  plates  pecul- 
iar to  most  Ophiurans,  though  there  are  irregular  plates 
which  may  be  vestiges  under  a  thick  skin.  The  arms  are 
without  spines.  In  some  species  of  Astrophyton  there 
are  no  oral  shields,  while  there  may  be  one  madreporic 
body  or  five. 


ECHINOIDEA. 

The  primitive  rocks  of  the  Lower  Silurian  formation 
have  yielded  a  primitive  sea  urchin  whose  marked  sim- 
plicity of  structure  offers  a  sufficient  reason  for  consider- 
ing it  as  an  ancestral  form.  This  urchin,  Bdthriocidaris 
pahle?ii  Schmidt,  by  name  (PI.  314,  fig.  i,  enlarged  twice), 
has  a  globular  corona  (popularly  called  shell)  with  the 
mouth  in  the  middle  of  the  lower  or  abactinal  side  and 
the  anus  opposite.  It  has  a  small  number  of  simple 
spines,  a  few  of  which  are  seen  attached  in  the  figure. 
The  spines  are  only  4  mm.  long  and  are  therefore  not  of 
disproportionate  length.  The  ambulacra  are  the  first 
areas  to  be  developed,  around  the  oral  disc  or  peristome 
(fig.  2) ;  they  are,  therefore,  of  primary  importance,  while 
the  interambulacra  arise  secondarily  in  the  spaces  between 
the  ambulacra.  Beginning  at  the  center  of  the  actinal 
area  it  is  seen  that  there  are  two  complete  circles  of 
ambulacral  plates  extending  around  the  mouth,  then 
comes  a  circle  of  ten  ambulacral  plates  and  five  interam- 
bulacra 1  plates  not  wholly  seen  in  fig.  2,  i' .  The  ambu- 
lacral plates  are  pierced  by  two  holes  which  are  separated 
by  a  partition.  It  is  seen  that  each  ambulacrum  origi- 
nates in  two  plates,  while  each  interambulacrum  arises 
from  one  plate.  This  stage  is  permanent  throughout  the 


172  SYNOPTIC    COLLECTION. 

life  of  Bothriocidaris.  It  is  a  primitive  and  an  extremely 
important  stage,  illuminating  the  otherwise  obscurely 
complex  structure  of  the  specialized  Echinoidea.  For 
this  reason  it  is  called  by  Dr.  Robert  T.  Jackson  the 
protechinus  stage.1 

As  we  have  already  said,  the  anus  is  opposite  the 
mouth.  It  is  surrounded  by  plates,  outside  of  which  are 
ten  terminal  plates  of  the  ambulacral  and  interambulacral 
areas.  Each  ambulacrum  and  interambulacrum  ends  in 
one  plate  but  none  of  these  plates  have  pores.  Thus  it 
is  seen  that  there  is  little  differentiation  of  the  abactinal 
area  from  the  corona  proper. 

Summing  up  the  distinguishing  characters  of  this 
ancient  Echinoid  we  have  the  following:  —  A  small 
number  of  plates  in  the  globular  corona ;  slight  differen- 
tiation of  the  actinal  and  abactinal  areas  from  the  corona 
proper ;  a  small  number  of  simple  spines. 

If  now  we  come  to  the  present  time  and  examine  Goni- 
oridaris  canaliculata  A.  Ag.,  we  find  in  the  young  (PI. 
315,  fig.  i  ;  fig.  2,  side  view  of  same)  some  instructive 
structural  features. 

Around  the  mouth  is  a  circle  of  ambulacral  plates, 
while  the  circle  next  to  this  one  has  ten  ambulacral  plates 
(fig.  i)  and  five  interambulacral  plates  (fig.  i,  /)  as  in 
Bothriocidaris.  Therefore  it  is  true  that  each  ambulacrum 
in  Goniocidaris  arises  from  two  plates,  and  each  interam- 
bulacrum from  one  as  in  the  ancient  genus. 

The  individual  plates  of  the  ambulacra  are  hexagonal 
and  nearly  on  a  level  with  the  hexagonal  interambulacral 
plates  as  in  Bothriocidaris,  but  unlike  this  genus  each  plate 
has  only  one  pore. 

The  similarity  in  structure  between  the  young  Goniocid- 
aris and  the  adult  Bothriocidaris  is  striking  and  of  value 


1  We  are  indebted  to  Dr.  Jackson  for  many  of  our  figures  and 
facts  concerning  fossil  Echinoidea.  See  Bull.  Geol.  Soc.  Amer., 
VII,  1896,  pp.  135-170;  also  pp.  171-254. 


METAZOA  —  ECHINODERMA.  173 

from  a  phylogenetic  point  of  view.  As  Goniocidaris 
grows  older,  two  rows  of  interambulacral  plates  arise  from 
the  single  plate  (fig.  i,  i,  2 ;  also  fig.  2)  so  that  there  are 
two  rows  of  ambulacral  plates  alternating  with  two  rows 
of  interambulacral  plates.  The  ambulacral  plates  become 
differentiated  and  are  lower  than  the  pentagonal  interam- 
bulacral plates,  while  each  plate  has  two  pores. 

The  adult  Goniocidaris  never  goes  beyond  the  stage  rep- 
resented by  the  two  rowed  ambulacra  and  interambulacra. 

Correlated  with  this  simplicity  of  external  structure  we 
have  a  primitive  mode  of  development.  In  other  words, 
Goniocidaris  develops  from  the  egg  without  passing 
through  a  metamorphosis. 

We  have  already  seen  that  while  a  few  starfishes  develop 
in  a  primitive  way,  most  of  them  pass  through  a  complex 
metamorphosis.  The  early  stages  "of  Echinoids  that  under- 
go such  a  transformation  are  similar  to  those  of  starfishes. 
The  embryo  or  pluteus  has  eight  arms  and  is  bilaterally 
symmetrical.  The  metamorphosis  of  the  Echinoid,  how- 
ever, is  accomplished  very  rapidly.  "In  less  than  an 
hour,"  according  to  Bury,1  "a  perfect  Pluteus  is  trans- 
formed into  a  small,  rounded  Echinoid  in  which  radiate 
symmetry  entirely  replaces  the  bilateral  symmetry  of  the 
larva." 

The  internal  structure  of  the  young  Goniocidaris  is 
primitive.  For  a  time  the  intestine  is  a  closed  tube,  there 
being  no  mouth  nor  anus.  During  this  period  the  animal 
takes  no  food,  and  moves  about  by  five  provisional  tube 
feet.  It  is  later  that  the  eating  apparatus  is  developed 
which  causes  a  modification  of  the  oral  area  and  a  resorp- 
tion  of  some  of  the  plates  of  the  corona ;  finally  the  intes- 
tine breaks  through  the  anal  disc. 

The  genus  Cidaris  (No.  316,  C.  thouarsi  Val.,  with 
spines;  No.  317,  without  spines)  when  young  possesses 
the  circle  of  ventral  plates  entire,  and  also  the  primitive 

1  Quart.  Journ.  Micr.  Soc.,  XXXVIII,  1895,  p.  77. 


174  SYNOPTIC    COLLECTION. 

condition  of  the  two  rowed  ambulacra  and  the  one  rowed 
interambulacra.  Later  some  of  the  ventral  plates  are 
resorbed  causing  more  or  less  irregularity  in  the  shape 
of  those  that  are  left,  while  the  tv\o  rowed  interambulacra 
arise  and  remain  essentially  unchanged. 

The  ambulacra  of  the  adult'  are  narrow  with  a  single 
nearly  vertical  row  of  paired  pores.  The  interambulacra 
on  the  other  hand  are  broad  and  carry  the  primary  spines 
which  are  large  and  few  in  number. 

The  anus  is  somewhat  raised  above  the  anal  disc. 
Surrounding  the  latter  is  the  ring  of  genital  and  ocular 
plates,  the  genitals  pointing  outward  and  the  triangular 
ocular  plates  inward. 

The  spines  of  this  species  are  cylindrical.  Some  are 
young  and  short  with  distinct  vertical  ridges  on  the  sur- 
face, while  the  older  ones  are  long  and  are  entirely  cov- 
ered with  a  growth  of  algae,  etc.  Very  different  from 
these  are  the  modified  spines  which  are  found  on  the 
abactinal  surface  of  the  corona  and  which  also  crowd  the 
actirial  area.  These  are  like  short,  stout,  flattened  clubs. 

It  has  been  seen  that  the  Cidaridae  of  the  present  era 
retain  in  their  youth  many  of  the  primitive  characters  of 
the  ancestral  Bothriocidaris.  The  changes  that  convert 
the  young  into  the  adult  are  an  increase  in  the  number  of 
coronal  plates,  the  differentiation  of  the  actinal  and  abac- 
tinal areas  from  the  rest  of  the  corona  and  the  modifica- 
tion of  the  spines. 

While  the  Cidaridae  represent  one  division  of  ancient 
Echinoids,  another  and  more  specialized  division  includes 
the  Melonitidae.  The  generalized  members  of  this  family 
are  Rhoechinus  and  Palaeechinus,  and  the  specialized  are 
Oligoporus  and  Melonites. 

Although  there  is  a  slight  overlapping  of  the  ambu- 
lacral  plates  in  Rhoechinus,  as  seen  in  PI.  318,  fig.  i,  owing 
to  the  fact  that  these  plates  are  not  united  along  their 
edges,  still  they  may  be  said  to  extend  across  one  half  of 
the  ambulacral  area  as  in  the  ancestral  form  so  that  only 
two  rows  of  ambulacral  plates  exist. 


METAZOA ECHINODERMA.  175 

The  number  of  rows  of  plates  in  the  interambulacral 
areas  of  the  simplest  species  of  .this  genus  is  four,  and  of 
the  most  specialized  eight. 

The  adult  Palaeechinus  gigas  McCoy,  has  the  primitive 
ambulacral  plates,  «,  <£,  on  the  margin  of  the  ambulacral 
area  (PL  318,  fig.  2,  shows  a  portion  of  one  ambulacrum ; 
b,  primitive  plate;  a  not  drawn),  while  two  other  plates 
have  arisen  (a1,  b1).  The  interambulacrum  has  from  five 
to  six  or  seven  rows  of  plates ;  six  are  clearly  shown  by 
the  red  dotted  lines  in  fig.  3.  This  drawing  begins  at  the 
point  of  origination  of  the  fifth  row  of  plates,  those  below 
this  point  not  being  preserved  in  the  specimen.  The  fig- 
ure shows  that  the  columns  5  and  6  originate  in  a  single 
plate  as  we  have  already  seen  is  the  case  with  the  inter- 
ambulacral rows  of  Bothriocidaris.  The  initial  plate  is 
always  near  a  seven-sided  or  heptagon  plate  (fig.  3,  JT). 
In  Palaeechinus  the  anal  disc  is  surrounded  by  the  ring 
of  alternating  genital  and  ocular  plates ;  the  former  are 
pierced  by  three  holes  while  the  latter  have  two. 

When  we  pass  to  the  genus  Oligoporus  we  find  in  the 
young  as  represented  at  the  ventral  border  two  rows  of 
ambulacral  plates  (PI.  319,  fig.  i,  a,  b) ,  while  farther  up 
the  corona  the  adult  condition  of  four  plates  (fig.  i,  0,  b, 
a',  £';  fig.  2)  is  seen,  and  still  farther  up  new  plates  arise 

(fig-  2). 

The  number  of  rows  of  interambulacral  plates  has  in- 
creased to  nine  (fig.  3)  in  the  most  specialized  species  of 
this  genus  (^Oligoporus  danae  M.  &  W.). 

The  forms  we  have  already  described  lead  the  way  to  a 
better  understanding  of  the  complex  structure  of  Melo- 
nites  (No.  320,  a-d,  M.  multiporus  Norw.  &  Owen). 
These  fossils  are  occasionally  preserved  with  some  of  the 
spines  attached.  The  latter  are  small  (PI.  321,  fig.  i, 
magnified  6+  diameters)  and  when  not  fastened  are  some- 
times found  in  the  hollows  of  the  corona. 

The  ventral  border  of  the  shell  (see  No.  320,  a,  b\  PI. 
321,  fig.  2)  shows  the  ambulacra  and  interambulacra. 


176  SYNOPTIC    COLLECTION. 

The  .ambulacra  arise  from  four  plates  (PI.  321,  fig.  2,  a, 
b,  a\  b1 ;  fig.  3,  ambulacrum  enlarged,  a,  b,  a',  b1).  This 
would  indicate  that  in  the  development  of  Melonites  the 
adult  condition  of  Bothriocidaris,  in  which  the  ambulacra 
consist  of  two  rows  of  plates,  has  been  skipped  by  the  law 
of  acceleration  in  development,  and  that  the  four-plate 
stage  is  homologous  with  the  adult  of  Oligoporus,  as 
pointed  out  by  Jackson,  or  it  may  be,  as  suggested  by  this 
investigator,  that  the  ambulacrum  of  Melonites  starts  with 
two  plates  which  might  be  seen  in  the  young  could  such 
specimens  be  obtained.  If  this  is  the  case  these  plates 
have  been  resorbed  during  the  growth  of  the  animal. 

New  rows  of  plates  are  added  between  those  already 
formed  (PI.  321,  fig.  3,  c,  d,  and  e,f) ,  so  that  each  ambu- 
lacrum becomes  more  complex  than  any  so  far  described. 
A  cross  section  of  an  ambulacrum  (fig.  4,  magnified  2 
diameters)  shows  the  relative  thickness  of  the  four  ambu- 
lacral  plates,  and  also  proves  the  fact  that  the  holes  pass 
diagonally  and  not  straight  through  the  shell.  The  dotted 
portions  of  the  pores  are  reconstructions,  these  parts  not 
being  clearly  shown  in  the  section. 

The  interambulacrum  (No.  320;  also  PI.  321,  figs.  2, 
5)  apparently  arises  from  two  plates  as  seen  in  the  speci- 
mens (No.  320,  the  dotted  lines  beginning  in  two  plates; 
also  seen  in  PI.  321,  figs.  2,  5).  According  to  Jackson  it 
is  most  probable  that  this  area  originates  in  one  plate, 
which  later  was  resorbed.  With  the  growth  of  the  animal 
the  interambulacrum  becomes  complicated  by  the  addi- 
tion of  a  number  of  rows  (fig.  5).  This  diagram  repre- 
sents the  ideal  arrangement  of  plates  in  one  interambula- 
crum as  determined  by  prolonged  and  critical  observation 
of  a  large  number  of  specimens.  The  theoretical  plate  /' 
is  included  in  the  figure  to  indicate  all  the  possible  plates 
the  interambulacrum  had  at  any  period  of  growth.  This 
plate  is  resorbed  in  the  adult,  as  already  stated.  Eight 
rows  are  found  most  commonly.  As  these  rows  approach 
the  anal  area  the  mechanical  necessity  of  the  case  com- 


METAZOA  —  ECHINODERMA.  177 

pels  them  to  be  drawn  out  and  to  diminish  in  number 
while  at  the  same  time  the  plates  themselves  become 
more  or  less  rhombic  in  form. 

The  lines  x,  y,  z  in  PI.  321,  fig.  5,  bisect  eight  rows, 
and  indicate  by  their  narrowing  angle  the  stringing-out 
arrangement  of  the  plates  in  this  area  (Jackson) .  This 
reduction  does  not  seem  to  be  comparable  to  the  dying 
out  of  parts  or  organs  so  characteristic  of  gerontic  forms. 
As  Dr.  Jackson  aptly  says,  it  may  be  compared  to  a  flock 
of  sheep  coming  through  a  narrow  pass.  The  small 
number  in  the  pass  does  not  mean  that  the  flock  is  les- 
sening, but  that  no  more  can  get  through  at  once.  If 
this  were  a  gerontic  condition  we  should  expect  to  find 
the  middle  or  latest  formed  rows  disappearing  first  and 
not  the  lateral  or  primary  rows.  This  is  the  case  in  the 
few  gerontic  specimens  observed  (see  below). 

If  now  a  graphic  summary  of  our  knowledge  of  the 
development  of  the  ambulacra  of  the  Palaeozoic  Echini 
be  given  (PI.  322,  A-G)  it  will  show  at  a  glance  that  the 
primitive  and  fundamental  simplicity  of  Bothriocidaris 
(A)  has  given  rise  through  progressive  steps  represented 
by  Rhoechinus  (B),  Palaeechinus  (C),  and  Oligoporus  (D 
at  ventral  border,  E  at  ambitus)  to  the  complexity  of 
Melonites  (F  at  ventral  border,  G  at  ambitus).  Dotted 
lines  are  drawn  through  the  primary  plates  a,  b  in  each, 
and  also  through  the  secondary  plates  a\  tf.  New  plates 
begin  to  appear  between  these  in  Oligoporus  (E)  and 
probably  constitute  the  rows  c,  d  in  Melonites  near  the 
ventral  border  (PI.  321,  fig.  3),  while  at  the  ambitus  ten 
rows  are  found.  The  remarkably  large  #nd  fine  speci- 
men of  Melonites  gigantcus  Jackson  (Pi.  323,  photo- 
graph) shows  still  greater  specialization  than  Melonites 
multiporus.  There  are  twelve  rows  of  ambulacral  and 
eleven  of  interambulacral  plates.  The  interambulacral 
area  (PI.  323,  fig.  2,  at  the  right)  is  especially  interesting, 
since  it  shows  a  tendency  toward  specialization  by  reduc- 
tion. The  last  formed  row  of  plates  (n)  has  died  out 


178  SYNOPTIC    COLLECTION. 

completely  before  reaching  the  anal  area.  Only  a  few 
specimens  with  this  specialized  character  have  been 
observed.  In  this  species  the  new  rows  are  introduced 
early  in  life,  showing  that  the  law  of  acceleration  in 
development  is  in  operation.  The  Melonite  form  is  also 
much  more  pronounced  than  in  Melonites  multiporus. 

The  anal  disc  of  Melonites  is  surrounded  by  the  ring  of 
alternating  genital  and  ocular  plates.  The  five  genital 
plates  can  seldom  be  seen  in  specimens  although  well 
preserved  in  No.  320.  These  plates  are  pierced  by  holes, 
while  the  ocular  plates,  according  to  Jackson,  are  without 
perforations. 1 

It  is  seldom  that  the  history  of  a  group  can  be  made 
out  by  the  study  of  a  portion  of  the  adult  of  a  single 
genus,  but  we  have  already  seen  that  such  is  the  case 
with  Melonites.  The  primitive  condition  of  Bothrioci- 
daris,  the  successive  progressive  stages  of  Rhoechinus, 
Palaeechinus,  and  Oligoporus  are  all  represented  in  the 
ventral  border  and  in  one  ambulacral  and  one  interambu- 
lacral  area  of  Melonites.  Nor  is  this  all;  the  greater 
specialization  by  the  process  of  reduction  is  illustrated  by 
a  few  specimens  of  this  genus. 

We  have  seen  that  Goniocidaris  and  Cidaris  are 
among  the  most  primitive  of  living  Echinoids.  Alexander 


1  Meek  and  Worthen  (Geological  Survey  of  Illinois,  II,  1866,  p. 
228)  state  that  the  ocular  plates  of  Melonites  multiporus  M.  &  W., 
are  without  any  traces  of  pores,  and  the  figures  are  drawn  without 
them.  In  a  footnote,  however,  they  add,  since  the  above  was 
written,  we  have^  examined  "another  fine  specimen  showing  the 
disc.  In  this  there  are  four  ovarian  pores  in  three  plates,  and 
three  in  each  of  the  other  two,  while  in  two  of  the  ocular  pieces 
there  is  apparently  a  single  pore  near  one  side." 

Roemer  figures  the  oculars  with  two  pores  (see  Arch.  f.  Naturg., 
I,  1855,  pl..xii,  fig.  4).  In  the  text  he  says,  p.  322,  "The  number  and 
position  of  the  pores  in  these  [ocular  plates]  cannot  be  recognized 
with  complete  certainty,  yet,  there  are  apparently  two  of  them  in 
each  plate  and  at  the  same  height  as  those  in  the  larger  plates"  [geni- 
tal plates]. 


METAZOA  —  ECHINODERMA.  179 

Agassiz  l  has  shown  that  the  young  of  all  other  Echini 
have  the  general  characteristics  of  these  primitive  forms. 
They  all  agree  in  having  a  small  number  of  plates  in  the 
corona,  slight  separation  of  the  actinal  and  abactinal 
areas  from  the  corona  proper,  nearly  vertical  rows  of 
paired  pores,  and  a  few  spines  of  disproportionate  length. 
Having  this  common  origin  we  shall  see  what  variations 
arise  in  the  adults  of  a  number  of  species. 

In  Arbacia pustulosa  Gray  (No.  324),  the  actinal  area 
is  large  and  the  ambulacra  are  broad  at  the  starting 
point,  growing  narrower  as  they  reach  the  edge  or  ambi- 
tus. The  interambulacra,  on  the  other  hand,  are  narrow 
at  the  ventral  border  and  broader  towards  the  ambitus. 
The  pores  preserve  their  primitive  character,  being  in  sim- 
ple vertical  rows.  The  anal  disc  in  this  species  consists 
of  five  plates ;  around  these  is  the  ring  of  five  genital 
plates  which  are  developed  after  the  anal  disc.  The  ocu- 
lars are  crowded  outside  of  this  ring  and  fit  into  the  places 
left  by  the  outer  angles  of  the  genitals.  This  genus  is 
interesting  for  the  fact  that  its  spines  never  become  artic- 
ulated but  remain  in  the  more  primitive  condition  of  the 
unjointed  spines  of  the  starfish. 

In  Diadema  setosum  Gray  (Nos.  325,  326),  the  nearly 
vertical  row  of  pores  in  the  narrow  ambulacra  becomes 
changed  during  the  growth  of  the  animal  into  nearly  ver- 
tical arcs  of  three  or  four  pairs  of  pores.  The  corona  is 
thin  with  broad  interambulacra.  The  actinal  area  is 
membranous  with  well  developed  teeth.  The  anal  disc 
(No.  326)  is  also  membranous  and  flexible,  with  the 
anus  raised  on  a  tube  near  the  center.  According  to 
A.  Agassiz  2  this  anal  tube  is  as  prominent  in  the  young 
as  the  anal  tube  of  some  species  of  Comatulae.  Three  of 


1  Palaeontological  and  Embryological  Development,  Proc.  Amer. 
Assoc.  Adv.  Sci.,  XXIX,  1880,  p.  389;  also  consult  review  of  the 
same  by  E.  D.  Cope,  Amer.  Nat.,  Oct.,  r88o,  p.  725. 

2Rev.  of  Echin.,  Mem.  Mus.  Comp.  Zool.,  Ill,  1872,  p.  276. 


180  SYNOPTIC    COLLECTION. 

the  ocular  plates  join  the  membranous  disc,  and  separate 
the  genital  plates,  while  the  other  two  which  are  each  side 
of  the  madreporic  plate  are  crowded  outside  of  the  ring  so 
that  they  do  not  touch  the  anal  membrane. 

The  slender  spines  of  the  adult  (No.  325)  are  usually 
more  or  less  solid  though  in  youth  they  are  hollow.  They 
vary  in  size,  the  smaller  ones  being  light  colored  and  the 
large  ones  dark  with  longitudinal  ridges.  These  ridges 
are  provided  with  short  pointed  teeth,  so  that  one  cannot 
pass  the  finger  downward  from  the  tip  end  of  the  spine  to 
its  base  without  being  pricked  by  the  sharp  points. 

Echinothrix  turcarum  Ret.  (No.  327),  has  the  pores 
in  arcs  of  three  pairs  similar  to  those  of  Diadema,  but 
unlike  this  genus  the  arcs  are  independent  of  each  other. 
The  ambulacra  broaden  out  slightly  on  the  abactinal  sur- 
face, suggesting  the  petaloid  condition  of  the  more  special- 
ized Clypeastroids. 

The  ambulacral  areas  are  crowded  with  many  small 
spines,  while  the  longer  and  more  delicate  ones  are  on  the 
interambulacra. 

Colobocentrotus  atratus  Br.  (No.  328),  is  peculiarly 
modified  in  the  shape  of  its  corona  and  spines.  The  ven- 
tral side  of  the  former  is  very  flat  and  the  dorsal  part  rises 
like  a  low  dome.  The  closely  set,  dark  colored  spines, 
like  tiles  in  a  pavement,  cover  this  dome,  completely  con- 
cealing everything  beneath.  If  these  spines  are  removed 
the  low  rounded  tubercles  are  seen  (No.  328).  The  ven- 
tral surface  is  covered  with  short  cylindrical  spines 
crowded  closely  together.  From  the  ambitus  the  long 
spines  resembling  clubs  extend  downward  causing  the  sea 
urchin  to  look  as  though  it  were  mounted  on  many  stilts. 
It  is  these  spines  that  mask  the  real  shape  of  the  corona, 
making  the  dome  appear  much  higher  than  it  really  is. 

In  spite  of  the  close  pavement  of  spines  there  are  many 
tube  feet  in  the  ambulacral  areas ;  these  are  arranged  in 
arcs  of  six  or  seven  pairs. 

The  young  Heterocentrotus  mammillatus  Br.   (No.  329), 


METAZOA ECHINODERMA.  181 

shows  the  dark  pavement  spines  finely,  especially  on 
the  dorsal  side.  Among  these,  on  the  ventral  side,  are 
spines  similar  to  those  on  which  Colobocentrotus  stands. 
The  longest  club-shaped  spines  extend  outward  from  the 
sides  of  the  corona,  while  young  ones  are  seen  just  growing 
from  the  upper  surface.  In  the  adult  (Nos.  330,  331)  the 
pavement  spines  have  longer  cylindrical  stems  by  which 
they  are  attached,  while  the  great  club-shaped  spines  have 
become  formidable  organs  of  defence.  The  size  of  these 
organs  is  correlated  with  the  increased  thickness  of  the 
corona.  The  oral  area  is  large,  having  encroached  upon 
the  corona.  The  ambulacra  are  broader  on  the  lower 
side  than  the  interambulacra,  while  above  the  ambitus 
they  are  narrow,  and  the  pores  are  in  narrow  arcs  of  num- 
erous pairs. 

Our  common  sea  urchin,  Strongylocentrotus  drobachi- 
ensis  A.  Ag.  (PI.  332  ;  No.  333,  two  spiny  specimens  and 
a  preparation  of  the  shell),  has  the  corona  made  of  two 
rowed  ambulacra  and  interambulacra.  Each  ambulacrum 
begins  in  the  young  with  two  plates,  as  shown  in  PI.  332, 
fig.  i,  and  each  interambulacrum  in  one  plate  (fig.  i,  i'). 
As  the  urchin  grows  older  a  portion  of  the  ventral  border 
is  resorbed,  as  shown  in  fig.  2,  and  the  oral  area  is  mem- 
branous and  spineless.  No  new  rows  of  plates  are  added 
in  either  the  ambulacra  or  interambulacra,  so  that  there 
are  only  twenty  rows  of  plates  in  all.  These  are  shown 
in  the  admirable  preparation  (No.  333),  where  each  indi- 
vidual plate  has  been  separated  and  mounted.  The 
ambulacral  plates  show  the  arcs  of  pores  which  vary  but 
usually  consist,  of  four  or  five  pairs.  These  have  arisen 
from  the  unbroken  vertical  rows  of  pores  of  the  young. 

The  anal  disc  is  seen  to  the  right,  made  of  tiny  plates 
which  are  placed  together  with  considerable  irregularity; 
a  little  to  one  side  of  the  center  is  the  anus.  The  last 
plate  terminating  each  interambulacrum  is  a  genital,  the 
largest  of  which  is  the  madreporic  body ;  an  ocular  plate 
is  at  the  tip  end  of  each  ambulacral  area.  The  five  geni- 


182  SYNOPTIC    COLLECTION. 

tals  and  the  two  oculars  form  the  ring  around  the  anal 
disc,  the  other  three  oculars  being  crowded  outside  the 
ring. 

The  globular  form  and  melon-like  aspect  of  Echinus 
melo  Lam.  (No.  334),  are  striking.  These  melon-like  sec- 
tions mark  off  distinctly  the  five  ambulacral  and  five  inter- 
ambulacra]  areas. 

The  plates  of  the  anal  area  are  numerous,  small,  and 
irregular,  while  the  five  ocular  plates  are  all  crowded  out- 
side of  the  ring. 

The  spines  of  Echinus  acutus  Lam.  (No.  335),  are  far 
removed  from  those  of  primitive  and  embryonic  forms, 
being  small,  short,  and  similar  on  both  ambulacra  and  in- 
terambulacra.  In  this  specimen  the  tube  feet  are  seen 
extending  from  the  shell. 

IRREGULAR  SEA  URCHINS. — CLYPEASTROIDS. 

Pygaster  patelliformis  Ag.  (No.  336),  is  one  of  the 
primitive  Clypeastroids.  The  corona  is  dome-shaped 
above  and  flattened  below,  resembling  the  regular  sea 
urchins.  The  mouth  is  placed  near  the  center  of  the 
oral  area,  but  the  anus  is  not  directly  opposite  as  in  the 
sea  urchins  so  far  examined.  It  extends  from  near  the 
apical  disc  to  the  margin  and  is  large  in  size.  The  ambu- 
lacral areas  are  narrow  with  simple  vertical  rows  of  paired 
pores,  while  the  interambulacra  are  broad. 

Young  Clypeastroids  in  general  possess  a  small  number 
of  plates  in  the  globular  corona,  a  few  large  spines  and 
tubercles,  simple  vertical  rows  of  pores  with  no  petal-like 
pattern  on  the  dorsal  side.  Internally  there  are  no  parti- 
tions. With  age  the  corona  becomes  more  flattened,  the 
number  of  plates  increases,  the  spines  grow  smaller,  and 
the  pores  form  into  petals,  proving  that  the  petaloid  con- 
dition is  a  specialized  one ;  and  that  the  sea  urchins  pos- 
sessing it  should  be  placed  after  those  whose  pores  are  in 


METAZOA ECHINODERMA.  183 

vertical  rows  or  in  arcs.  The  internal  partitions  so  char- 
acteristic of  the  irregular  sea  urchins  are  found  in  the 
adult,  sometimes,  however,  in  a  rudimentary  condition. 

The  typical  characteristics  of  the  first  division  of  the 
irregular  sea  urchins  are  well  shown  in  Clypeaster  sub- 
depressus  Ag.  (No.  337),  and  for  this  reason,  it  would 
seem,  the  name  of  Clypeastroids  is  given  to  the  division. 
There  is,  however,  no  well  defined  line  between  this 
group  and  the  next,  the  Spatangoids,  so  that  it  seems 
better  to  place  both  under  the  head  of  the  irregular  sea 
urchins. 

The  corona  of  Clypeaster  is  flattened  and  longer  than 
it  is  broad.  It  can  be  so  placed  as  to  bring  the  odd  am- 
bulacral  petal  in  the  median  line,  and  the  remaining  two 
pairs  of  petals  on  either  side,  thus  dividing  the  test  into 
two  nearly  equal  parts. 

The  mouth  is  near  the  middle  of  the  lower  side  and  the 
simple  ambulacral  grooves  extend  outward  from  it.  There 
are  delicate  spines  in  the  grooves,  and  stronger  ones  on 
top  of  the  conspicuous  petals  when  these  are  formed. 

The  anal  system  has  moved  from  the  upper  to  the 
lower  side,  near  the  margin,  and  the  anus  is  seen  in  No. 
337,  so  that  the  Clypeastroid  has  an  anterior  and  a  pos- 
terior end. 

The  abactinal  area  is  far  more  indefinite  than  in  the 
regular  urchins.  It  is  made  up  partly  of  the  madreporic 
body  which  is  in  the  center.  Four  or  five  genital  open- 
ings are  seen,  but  the  plates  themselves  do  not  appear. 

If  the  upper  portion  of  the  test  is  removed  (No.  337), 
the  immense  jaws  with  two  teeth  are  exposed.  These 
jaws  consist  of  five  strong  parts  which  taken  together  con- 
stitute a  powerful  eating  apparatus.  The  upper  and  lower 
parts  of  the  shell  are  connected  by  slender  pillars  (No. 
337)  which  are  an  important  characteristic  of  the  Clype- 
astroids, the  regular  sea  urchins  having  nothing  of  the 
kind.  Around  the  outer  edge  these  pillars  unite,  forming 
more  or  less  open  walls,  as  seen  in  No.  337  where  a  por- 
tion of  the  edge  has  been  removed. 


184  SYNOPTIC    COLLECTION. 

Sometimes  the  ambulacral  petals  take  up  the  greater 
part  of  the  upper  surface  of  the  corona,  as  is  the  case  with 
Echinanthus  rosaceus  Gray  (Nos.  338-340).  The  central 
portion  of  each  petal  is  raised  while  the  furrows  of  the 
pore-bearing  zones  are  sunken,  making  the  rosette  most 
conspicuous.  Here,  as  in  Clypeaster,  the  madreporic 
body  is  in  the  center.  Joined  to  it  are  the  ocular  plates 
perforated  for  the  ocular  pores  (not  seen  in  No.  339), 
while  beyond  it  are  the  genital  plates  with  their  openings 
(No.  339).  The  spines  of  this  genus  are  small  as  are 
most  of  the  Clypeastroids.  When  removed  as  in  No.  339 
the  tubercles  are  seen  to  be  much  reduced  in  size  from 
the  regular  urchins.  The  vertical  section  (No.  340)  ex- 
hibits the  powerful  jaws  and  the  massive  pillars  of  the 
interior. 

Not  only  are  the  upper  and  lower  portions  of  the  test 
united  by  pillars  but  in  Laganum  depressum  Less.  (No. 
341),  there  are  walls  running  parallel  with  the  margin,  as 
seen  in  the  cross  section  (No.  342).  In  this  genus  the 
edge  is  much  thickened,  and  the  anus  is  on  the  lower  side 
quite  near  the  mouth. 

The  young  Echinarachnius  parma  Gray,  varies  in  form, 
but  in  No.  343  it  is  circular  and  somewhat  dome-shaped, 
while  in  other  specimens  it  is  elliptical.  No.  343,  a-e, 
has  light  colored  spines  attached.  There  are  two  rows 
of  these  on  both  the  ambulacra  and  interambulacra.  They 
are  short  and  delicate,  very  different  from  the  long  spines 
of  the  primitive  and  embryonic  regular  sea  urchins.  The 
youngest  specimen  (No.  343,  a)  is  without  a  distinct  am- 
bula'cral  pattern,  and  the  ambulacral  grooves  of  the  lower 
surface  are  scarcely  visible.  In  an  older  specimen  meas- 
uring 5.1  mm.  these  grooves  have  been  seen,  and  accord- 
ing to  A.  Agassiz  minute  pores  were  formed  in  them. 

The  mouth  is  near  the  middle  of  the  lower  side  pro- 
tected by  spines  above  (No.  343,  c)  and  sunken  within 
the  corona  are  the  five  horizontal  teeth.  The  anus  at 
this  stage  is  on  the  upper  side  a  short  distance  from  the 


METAZOA  —  ECHINODERMA.  185 

margin  (No.  343,  b),  while  the  madreporic  body  occupies 
the  usual  central  position  of  the  anal  area  as  seen  in  the 
regular  sea  urchins.  No.  343,  g,  has  been  bleached  by 
nature  and  through  the  microscope  the  openings  of  the 
madreporic  body  are  clearly  seen. 

As  the  sand-dollar  grows  older  it  becomes  flattened 
and  more  or  less  heart-shaped  (No.  343,  h-1).  The 
petals  become  distinct,  the  outer  ends  are  open,  and  the 
pores  extend  towards  the  ambitus,  but  do  not  reach  the 
edge.  At  this  time  the  internal  partitions  radiate  in  five 
pairs  from  the  edge  toward  the  center  and  there  are  few 
pillars. 

The  ambulacra  and  interambulacra  are  often  distinctly 
seen  in  these  younger  stages,  as  in  No.  343,  m  and  n, 
where  the  limits  of  the  individual  plates  can  be  easily 
traced ;  those  on  the  lower  surface  are  much  more 
irregular  than  those  above.  The  ambulacral  furrows  are 
simple  but  branch  at  their  outer  extremities.  Sometimes, 
as  in  No.  343,  p.  there  is  no  indication  whatever  of  these 
furrows. 

The  ocular  openings  at  the  ends  of  the  ambulacra  are 
large,  but  the  genital  plates  and  pores  cannot  be  detected. 

The  adult  (No.  343,  r,  s)  is  more  flattened  than  any  of 
the  Clypeastroids  and  is  covered  by  tiny,  dark  colored 
spines  (No.  343,  r).  It  is  usually  difficult  to  make  out 
the  ambulacral  and  interambulacral  plates,  but  if  the 
specimen  is  bleached  by  nature,  or  treated  with  acid  as  is 
the  case  with  No.  343,  s,  they  come  out  more  clearly. 
They  are  also  finely  seen  from  the  inside  when  the  dorsal 
side  is  removed.  The  ambulacral  furrows  are  well 
defined  and  branch  a  few  times.  The  petals  above  are 
large  with  furrows  between  the  holes ;  they  open  at  their 
outer  ends  in  very  flat  sand-dollars  while  in  more  convex 
specimens  they  nearly  converge.  A  few  pairs  of  pores 
extend  downward  from  the  petals  towards  the  edge 
(No.  343,  s). 

The  anus  has  moved  downward  to  the  edge  (No.  343, 


186  SYNOPTIC    COLLECTION. 

r,  s).  Around  the  madreporic  body  are  five  ocular 
openings  at  the  ends  of  the  ambulacra,  and  four  genital 
openings  at  the  ends  of  the  interambulacra.  The  inter- 
ambulacrum  opposite  the  odd  petal  is  without  a  pore. 
The  preparation  (No.  344)  shows  the  five  pairs  of  parti- 
tions which  radiate  from  the  edge  towards  the  center 
with  space  between  each  pair  of  partitions.  There  are 
other  pairs  that  occupy  the  interambulacral  areas  while 
many  pillars  are  crowded  together  on  the  ambulacra. 

Greater  specialization  of  structure  marks  the  species 
Echinarachnius  excentricus  Val.  (No.  345).  Here  the 
lower  side  is  marked  by  radiating  furrows  that  divide 
close  to  the  mouth  and  afterward  subdivide  and  send  their 
branches  over  to  the  upper  surface.  Three  of  the  petals 
are  larger  than  the  other  two,  and  the  mound  bearing  the 
rosette  is  not  in  the  center  but  nearer  the  posterior  end. 
The  anus  has  moved  from  the  edge  to  the  lower  side. 

Encope  grandis  Ag.,  when  young  is  circular  in  outline 
and  is  without  the  rosette  or  lunules.  The  adult  (No. 
346)  has  five  large  openings  into  the  margin  besides  the 
completed  lunule  in  the  median  interambulacrum.  The 
petals  of  the  rosette  differ  in  size  and  shape,  the  pos- 
terior pair  being  longer  than  the  others  and  extending 
nearly  to  the  lunules. 

The  madreporic  body  is  star-shaped  and  four  genital 
openings  are  at  the  tips  of  the  rays,  while  the  fifth 
opening  is  nearer  the  center.  The  five  ocular  pores  are 
at  the  angles  of  the  rays. 

In  conclusion  it  may  be  said  that  the  young  of  all  the 
Clypeastroids  are  much  more  like  Echinometra  and  the 
regular  sea  urchins  than  they  are  like  the  adults  of  their 
own  group.  This  is  sufficient  reason  for  placing  the 
Clypeastroids  next  the  regular  sea  urchins  and  before  the 
Spatangoids. 


METAZOA ECHINODERMA.  187 


IRREGULAR  SEA  URCHINS.  —  SPATANGOIDS. 

One  of  the  ancestral  forms  of  the  more  specialized 
division  of  the  irregular  sea  urchins  commonly  called 
Spatangoids  is  Pyri?ia  subsphaeroidalis  d'Orb.  (No.  347), 
in  which  the  test  is  high  and  dome-shaped  and  the  ambu- 
lacra are  arranged  in  the  primitive  fashion  of  vertical 
rows  from  mouth  to  apex.  The  mouth  is  nearly  central 
in  this  genus,  while  the  anus  is  on  the  dorsal  side  of  the 
posterior  part. 

The  young  forms  of  this  group  which  are  living  to-day 
are  similar  to  the  young  of  the  regular  urchins  and  of  the 
Clypeastroids.  In  fact  the  starting  point  of  these  groups 
is  the  same,  as  shown  by  A.  Agassiz.1 

The  Spatangoids  have  at  first  the  vertical  row  of  pores 
running  from  mouth  to  apex,  few  tubercles  of  large  size, 
spines  of  disproportionate  length  and  size,  and  a  simple 
lipless  mouth.  The  adults,  however,  carry  specialization 
much  farther  than  any  other  members  of  the  class. 

Beginning  with  the  more  generalized  forms  we  find 
Echinoneus  semihmaris  Lam.  (No.  348),  is  dome-shaped 
with  the  ambulacra  in  vertical  rows  and  no  petals  formed 
throughout  life.  The  mouth  is  near  the  center  and  as  in 
many  Spatangoids  is  without  teeth,  while  the  anus  in  this 
genus  is  between  the  mouth  and  posterior  end.  Four 
genital  and  five  ocular  pores  are  seen  in  the  abactinal 
area. 

In  addition  to  the  ordinary  tubercles  Echinoneus  has 
others  that  have  the  appearance  of  glass  and  carry  no 
spines. 

Hybodypus  caudatus  Wright  (No.  349),  is  a  small 
somewhat  flattened  urchin  with  the  three  anterior  ambu- 
lacra separated  from  the  two  posterior  ones.  Here 
the  mouth  has  moved  a  little  towards  the  anterior  side 
while  the  anus  is  in  a  depression  on  the  dorsal  side. 

1  Proc.  Amer.  Assoc.  Adv.  Sci.,  XXIX,  1880,  p.  397. 


188  SYNOPTIC    COLLECTION. 

Toxaster  oblongus  Deluc.  (No.  350),  is  longer  than 
broad  with  a  groove  at  the  anterior  end,  the  posterior  end 
being  high  with  the  anus  visible. 

Holaster  striato-radiatus  d'Orb.  (No.  351),  is  a  high 
dome-shaped  Spatangoid  with  simple  narrow  ambulacra 
and  broad  interambulacra.  The  mouth  is  at  the  anterior 
end  of  the  ventral  side  and  the  anus  at  the  posterior 
end.  The  abactinal  area  cannot  be  made  out  in  the 
specimen  but  the  boundary  lines  of  some  of  the  plates 
can  be  traced. 

Colly  rites  dorsalis  Ag.  (No.  352),  shows  more  plainly 
the  specialization  in  the  position  of  the  ambulacra,  three 
of  which  are  in  front  while  the  other  two  are  widely  sep- 
arated from  them.  This  drawing  out  of  the  abactinal 
area  in  an  antero-posterior  direction  has  caused  a  sep- 
aration in  the  genital  and  ocular  plates. 

No.  353  is  an  interesting  specimen  of  Micraster  from 
the  Lower  Greensand.  It  is  a  jasper  cast  in  which  the 
posterior  end  is  preserved.  The  partition  between  the 
paired  pores  is  clearly  shown  and  three  of  the  ambulacra, 
while  the  ornamentation  is  well  preserved.  This  genus 
is  usually  distinctly  heart-shaped  with  the  bilabiate  mouth 
placed  far  forward  and  the  odd  anterior  ambulacrum  in  a 
groove. 

Hemiaster  minimus  Desor  (No.  354),  when  young  has 
the  anus  nearly  central  and  the  test  has  much  the 
appearance  of  that  of  the  regular  urchins.  Marked 
changes  take  place,  however,  in  the  course  of  develop- 
ment. The  outline  of  the  urchin  becomes  more  irregular 
and  flattened,  and  some  of  the  ambulacral  plates  become 
modified  into  four  deep  cups  or  pouches  for  the  purpose 
of  holding  and  protecting  the  eggs.  Within  these  pouches 
the  embryos  develop;  by  the  law  of  acceleration  the  meta- 
morphosis is  skipped,  and  the  embryos  are  retained  by 
the  parent  until  the  plates  of  the  test  are  formed.  The 
adult  has  a  band  of  microscopic  tubercles  called  fascicles 
encircling  the  petals. 


METAZOA  ECHINODERMA.  189 

A  giant  among  its  kindred  is  Metalia  pectoralis  A. 
Ag.  (No.  355).  Some  of  its  spines  are  peculiarly  modi- 
fied, being  so  extremely  long  and  delicate  that  they  are 
rarely  preserved.  These  are  attached  to  small  areas  on 
each  side  of  the  dorsal  median  line  and  within  the  fasci- 
ole.  They  are  capable  of  lying  flat  upon  the  corona,  as 
seen  in  No.  355.  On  other  parts  of  the  body  the  spines 
vary  in  length  and  in  some  places  they  are  distinctly 
curved.  The  mouth  is  near  the  forward  end  and  the 
anus  in  the  large  blunt  posterior  extremity.  The  marked 
sexual  difference  in  size  is  shown  by  No.  355  ;  the  female 
is  much  larger  than  the  male,  while  the  latter  is  rarely 
found.  The  corona  denuded  of  spines  is  a  beautiful 
object  (No.  356). 

Another  large,  robust  urchin  is  Meoma  •ventricosa  Liitk. 
(No.  357,  ventral  side).  Here  similar  spines  cover 
the  whole  surface.  The  mouth  (No.  357)  has  a  large 
lip  and  the  anus  is  at  the  posterior  end  of  the  body.  The 
sunken  petaloid  ambulacra  above  are  conspicuous. 

Among  the  most  specialized  of  the  irregular  urchins  is 
Moira  atropos  Ag.  (No.  358).  Here  different  parts  of 
the  test  are  made  of  variously  shaped  plates.  The  mouth 
is  far  forward,  and  the  anus  is  at  the  upper  side  of  the 
blunt  posterior  end.  There  appear  to  be  deep  slits  on 
the  upper  side  and  on  looking  more  closely  the  ambu- 
lacral  pores  are  seen  at  the  bottom  of  four  slits.  The 
fifth  one,  which  is  more  like  a  groove  than  a  slit,  extends 
forward  and  turning  downward  reaches  the  mouth.  The 
young  are  carried  in  these  sunken  ambulacra  after  much 
the  same  fashion  as  in  Hemiaster.  The  variation  in  the 
shape  and  size  of  the  interambulacral  plates  is  great. 

An  extreme  of  specialization  is  reached  when  one 
examines  A mphidetus  cordatus  Ag.  (No.  359).  The  short 
silky  spines  (No.  359,  c)  conceal  the  ambulacra  and 
interambulacra  which  are  most  curiously  modified.  In- 
stead of  simple  vertical  rows  or  the  usual  rosette  of  petals 
there  is  here  a  star-like  arrangement  of  the  ambulacra 


190  SYNOPTIC    COLLECTION. 

(No.  359,  b,  d),  the  narrow  points  of  the  star  radiating 
downward  toward  the  ambitus  when  they  become  some- 
what obscure  only  to  reappear  on  the  ventral  side  (No. 
359,  b)  in  the  form  of  perforated  bands  which  reach  to 
the  mouth.  Between  these  bands  the  interambulacra 
are  set  in,  the  different  areas  and  the  individual  plates 
composing  them  varying  greatly  in  shape  and  size. 

The  mouth  (No.  359,  b)  is  at  the  anterior  end  with  its 
lip,  while  the  anal  disc  at  the  posterior  end  (No.  359,  a, 
test  of  a  younger  specimen  than  the  others)  is  perfectly 
preserved.  Below  this  anal  plate  there  is  another  with 
three  openings  on  either  side.  In  the  sunken  area  at  the 
top  are  four  openings. 

H  OLOTHUROIDEA . 

We  know  nothing  of  the  ancient  ancestral  Holothuroids 
excepting  by  the  minute  hard  parts,  —  spicules,  wheels, 
anchors,  etc.,  —  which  are  preserved  in  the  rocks. 
These  occur  no  farther  back  than  the  Carbonic  age 
(Zittel).  They  throw  little  light  upon  the  phylogenetic 
history  of  the  group,  and  therefore  we  must  turn  to  the 
primitive  forms  living  to-day. 

Among  the  deep-sea  Holothuroids  are  the  Elasipoda 
which  retain  the  characters  of  the  larva  in  the  adult 
stage  more  than  any  other  members  of  the  class. 
Accordingly  in  describing  the  adult  we  are  giving  the 
more  essential  larval  characteristics. 

Generally  speaking,  the  body  is  distinctly  bilateral 
(PI.  360,  figs.  1-4,  Elpidia  verrucosa  Theel.  and  Scotoph- 
anes  murrayi  Theel),  while  its  walls  are  provided  with 
simple  spicules  of  few  rays.  The  dorsal  part  of  the  body 
extends  in  front,  causing  the  mouth  to  turn  towards  the 
ventral  side  (see  figs.  2,  4)  instead  of  being  terminal. 
The  anus  is  dorsal  in  position  (fig.  i)  or  terminal  as  in 
Scotophanes  (fig.  4).  The  ventral  surface  is  flattened, 


METAZO  A  -  ECH  INODERMA  .  191 

consisting  of  two  ambulacra  (figs.  2,  4),  and  the  ambu- 
lacral  feet  with  sucking  discs  are  restricted  to  this  side 
and  extend  in  pairs  towards  the  posterior  end  of  the 
body  (rigs,  i,  2,  4).  On  the  dorsal  side  there  are  tubu- 
lar organs  which,  as  they  perform  a  different  function 
from  the  ambulacral  feet,  are  without  sucking  discs  (fig! 
3  ;  in  fig.  i  these  organs  are  broken  off,  but  the  four 
openings  on  the  anterior  part  of  the  body  show  their 
position). 

In  many  Elasipoda  the  water-vascular  system  com- 
municates with  the  exterior  by  means  of  the  madreporic 
body.  Moreover,  the  circular  ring  around  the  mouth  is 
made  up  of  simple  spicules  which  are  separated  from  one 
another. 

The  internal  respiratory  organs  lack  the  usual  tree-like 
form,  and  the  tentacles  are  few  in  number,  usually  not 
more  than  ten  in  the  Elpidiidae,  the  most  generalized 
family. 

While  the  Elasipoda  have  retained  the  larval  characters 
more  than  the  other  members  of  the  class,  still  we  cannot 
fail  to  see'what  The'el  l  has  already  pointed  out,  that  these 
Echinoderms  are  more  like  the  specialized  forms  of  most 
invertebrates  in  several  important  particulars.  They  are 
bilaterally  symmetrical.  They  have  a  distinct  antero- 
posterior  axis  and  a  ventral  side  differentiated  from  the 
dorsal.  They  have  a  small  number  of  locomotive  organs 
and  these  have  a  definite  position. 

The  remaining  families  of  Holothuroids  —  the  Pedata 
and  Apoda  —  when  young  resemble  the  Elasipoda. 
Most  of  these  forms  belong  to  the  shallow  waters  and 
they  have  become  greatly  modified  to  meet  widely  dif- 
ferent conditions. 

At  first  the  madreporic  body  opens  on  the  exterior,  but 
later  the  connection  is  lost  and  the  canal  ends  blindly  in 
the  interior. 


Rep.,  Zool.,  IV,  part  13,  1882,  p.  147. 


192  SYNOPTIC    COLLECTION. 

Pedata.  One  of  the  more  generalized  members  of  the 
Pedata  is  Holothiiria  tubulosa  Tied.  (No.  361,  model), 
in  which  the  body  exhibits  a  distinct  antero-posterior 
axis.  This  genus  has  the  feet  scattered  over  the  surface 
instead  of  being  arranged  in  rows. 

Another  representative  of  this  group  is  Pentacta  fron- 
dosa  Jaeger  (No.  362),  in  which  the  division  of  the  body 
into  five  distinct  areas  is  finely  shown.  Two  double  rows 
of  ambulacral  feet  extend  down  the  dorsal  side  and  three 
on  the  ventral  side.  There  are  also  dorsal  feet  in  the 
interambulacral  areas.  The  terminal  mouth  is  surrounded 
by  numerous  organs  resembling  tentacles  but  which  serve 
as  branchiae  or  external  gills.  The  madreporic  body  is 
internal.  The  anus  is  at  the  posterior  end,  and  the 
respiratory  tree  is  given  off  from  the  cloaca  near  the  vent. 
This  is  seen  in  No.  363  which  is  a  dissection  showing 
chiefly  the  digestive  and  reproductive  systems. 

A  peculiar  modification  of  structure  is  seen  in  Psolus 
fabrici  Semper  (=.Lophothuria  fabrici  Verr.)  (No.  364), 
where  the  lower  surface  is  converted  into  a  creeping-disc 
resembling  the  foot  of  a  gastropod.  It  has  three  rows  of 
ambulacral  feet  and  there  are  none  on  the  scaly  dorsal 
side. 

Cucumaria  crocea  Less.,  in  its  development  skips  alto- 
gether the  larval  stage  and  enters  upon  the  adoles- 
cent or  neanic  period.  The  young  of  Cucumaria  crocea 
Less.  (PI.  365,  fig.  i,  dorsal  side;  fig.  2,  ventral  side), 
were  found  by  Sir  Wyville  Thomson1  attached  to  the  two 
rows  of  ambulacral  feet  on  the  back  of  the  mother. 
They  were  all  "miniatures  of  their  parents,"  excepting 
that  their  dorsal  ambulacral  feet  were  in  an  undeveloped 
condition,  while  their  ventral  feet  were  early  and  well 
developed  and  used  for  clinging  to  the  parent.  The 
adult  like  the  larva  is  elongated  with  distinct  rows  of  feet 

iQtioted  by   Th^el   in  Chall.  Rep.,  Zoo!.,  XIV,  part  32,  1886, 
p.  60. 


METAZOA ECHINODERMA.  193 

extending  from  one  end  to  the  other.  The  mouth  and 
anus  are  both  terminal. 

Apoda.  The  reduction  of  parts  is  going  on  in  the 
group  to  which  Caudina  arenata  Stimp.  (No.  366), 
belongs.  The  young  and  adult,  both  seen  in  No.  366, 
are  similar  in  external  appearance.  The  rows  of  feet 
have  disappeared,  and  the  water-vascular  system  is,  there- 
fore, much  reduced.  Ludwig  has  shown  that  an  allied 
form,  Chirodota  rotifera  Pourtales,  has  a  stage  in  which 
it  loses  its  madreporic  body  and  the  stone  canal  detaches 
itself  from  the  dorsal  wall,  becoming  enclosed  within  the 
perisoma. 

The  most  specialized  of  all  the  Holothuria  is  Synapta 
(No.  367,  S.  glabra  Semper),  found  in  the  shallower 
waters  of  the  shore  region. 

The  body  has  become  modified  and  is  extremely  elon- 
gated. It  contains  spicules  in  the  shape  of  anchors  and 
plates.  The  feet  have  disappeared  and  the  radial  ambu- 
lacral  vessels  are  also  wanting,  so  that  the  water-vascular 
system  is  reduced  to  a  ring  around  the  mouth.  There  is 
no  respiratory  tree  and  altogether  the  genus  is  a  good 
illustration  of  specialization  by  reduction. 

To  recapitulate  briefly :  The  pre-Cambrian  ancestor  of 
the  Echinoderms  was  probably  free  swimming  and  may 
be  represented  by  certain  larvae  of  existing  Echinoderms. 
The  Palaeozoic  ancestors,  however,  were  with  little  doubt 
attached  forms.  Of  these  the  Cystoids  and  Blastoids 
had  a  more  or  less  globular  body  which  was  either  sessile 
or  fastened  by  a  stem.  The  body  was  covered  with 
plates  which  at  first  were  placed  together  irregularly  but 
in  later  forms  were  arranged  in  regular  circles.  The 
oral  surface  was  above  and  the  aboral  below.  By  the 
differentiation  of  areas  of  plates,  called  ambulacra,  and  of 
feathery  pinnules,  the  apparatus  for  catching  food  and 
carrying  it  to  the  mouth  became  more  efficient.  .Pores 
through  the  body  wall  admitted  water  to  the  respiratory 
organs  or  hydrospires. 


194  SYNOPTIC    COLLECTION. 

In  the  case  of  the  Crinoids  specialization  not  only 
brought  about  greater  regularity  in  the  body  plates  but 
arms  were  developed  ;  the  ambulacra  still  served  as  food 
grooves,  through  the  holes  of  which  numerous  pointed 
tentacles  were  put  out. 

The  digestive  system  in  these  ancient  Echinoderms 
was  distinct  from  the  body  cavity  and  its  two  openings  — 
mouth  and  anus  —  were  usually  on  the  upper  side. 

The  Asteroidea,  living  to-day,  pass  through  a  transient 
stage  in  their  development  when  they  are  attached.  In 
becoming  free  they  turn  over  so  that  the  oral  side  is 
below  and  the  aboral  above.  In  this  favorable  position 
for  obtaining  food  from  the  sea  bottom  by  means  of  the 
mouth,  the  pointed  tentacles  of  the  ambulacra  develop 
suckers  and  become  locomotive  organs  or  tube  feet.  It 
is  probable  that  further  specialization  causes  the  almost 
useless  ambulacra  of  the  Ophiuroidea  to  become  internal, 
and  the  equally  useless  tube  feet  to  take  on  reduced 
characters. 

Besides  the  ambulacral  plates  of  the  typical  Asteroidea 
there  are  rows  of  interambulacral  plates  on  the  ventral 
side,  while  the  dorsal  side  is  made  of  irregular  plates. 
The  digestive  system  is  complete,  but  in  most  cases  the 
anus  opens  opposite  the  mouth  on  the  dorsal  side. 

Water  is  admitted  to  the  body  cavity  of  the  Asteroidea 
through  a  sieve-like  organ  which  connects  with  a  series 
of  tubes  that  serve  the  double  function  of  respiration  and 
locomotion.  Greater  concentration  marked  the  organiza- 
tion of  the  Echinoidea.  The  ambulacral  and  interambu- 
lacral plates  of  the  typical  Asteroidea  here  reach  an 
extreme  development,  while  the  irregular  plates  have 
almost  wholly  disappeared. 

All  trace  of  a  fixed  stage  is  lost  in  the  ontogeny  of  the 
Echinoidea,  so  that  the  larvae  are  free  from  the  start. 

The  digestive  and  water-vascular  systems  are  similar  to 
those  of  the  typical  Asteroidea,  with  the  exception  of 
certain  specializations  such  as  the  eating  apparatus  or 
"teeth"  and  the  reduced  tube  feet  of  many  sea  urchins. 


METAZOA ECHINODERMA.  1 95 

The  Holothuroidea  like  the  Echinoidea  have  no  fixed 
stage  in  their  development.  As  has  been  said,  they 
resemble  the  more  specialized  invertebrates  in  being 
bilaterally  symmetrical  and  in  having  an  antero-posterior 
axis  of  the  body.  They  possess  many  reduced  characters  ; 
the  number  of  feet  is  limited,  and  the  water-vascular 
system  in  some  forms  is  a  mere  ring  around  the  mouth. 
This  reduction  is  indicative  of  specialization  and  it  offers 
a  reason  for  placing  this  group  farthest  from  the  primitive 
ancestral  form  of  Echinoderms. 


196  SYNOPTIC    COLLECTION. 

MOLLUSCA. 

Section  7. — PELECYPODA. 

The  arrangement  of  the  molluscs  in  the  Synoptic  Col- 
lection is  governed  by  the  same  principle  that  controls  the 
classification  of  the  preceding  subkingdoms.  We  con- 
sider first,  primitive  ancestral  Pelecypods  and  the  early 
stages  of  living  forms;  secondly,  the  specialization  of 
adults.  Since  a  fleshy  animal  antedates,  as  a  rule,  a  skel- 
eton-bearing animal,  as  we  have  seen  in  the  Protozoa, 
Porifera,  and  Coelentera,  and  since,  also,  fleshy  parts  are 
not  usually  preserved  in  the  geologic  formations,  we  turn 
to  the  embryonic  and  larval  stages  of  existing  species  to 
determine  so  far  as  possible  the  characters  of  the  ances- 
tral fleshy  forms.  On  the  other  hand,  since  the  skeleton 
or  shell  when  made,  is  a  comparatively  sure  guide  to  the 
structure  of  the  soft  parts,  we  regard  with  special  interest 
the  remains  of  the  primitive  Mollusca  in  the  Protozoic 
and  the  Palaeozoic  strata.  An  early  stage  of  the  pres- 
ent Pelecypod  larva  is  the  trochophore  (PI.  368).  It  is 
a  little  fleshy  creature  whose  distinctive  features  are  a  cil- 
iated locomotive  ring  (the  velum)  in  front  of  the  mouth, 
and  a  tiny  sac  or  shell  gland  on  the  dorsal  surface.  This 
sac  is  simply  a  portion  of  the  outer  wall  turned  inward, 
but  it  plays  an  important  part  since  it  is  soon  everted 
and  at  once  the  shell  begins  to  form  on  its  surface.  The 
latter  is  secreted  extremely  early  in  the  life  of  the  embryo, 
therefore  it  is  inherited,  and  of  value  phylogenetically. 
At  first  it  is  shaped  like  a  tiny  plate  or  cap.  and  therefore 
the  ancestor  from  which  the  Mollusca  descended  prob- 
ably possessed  such  a  shaped  shell.  In  the  case  of  the 
developing  Pelecypod  the  tiny  plate  forms  into  two  parts 
or  valves,  while  in  the  Gastropod  the  cap  becomes  a  cone 
and  later  a  new  shell  is  formed  which  in  most  cases 
becomes  a  spiral. 


METAZOA — MOLLUSCA.  197 

The  name  Pelecypoda  is  given  to  the  most  generalized 
class  of  molluscs  in  preference  to  Lamellibranchiata  for 
three  reasons,  viz.,  it  has  priority  over  the  latter  name ; 
it  is  in  uniformity  with  the  names  of  the  other  classes  of 
Mollusca  (Gastropoda,  Pteropoda,  Cephalopoda)  ;  the 
word  Lamellibranchiata  refers  to  the  gill  which  is  one  of 
the  most  variable  organs  of  a  mollusc,  while  Pelecypoda, 
Gastropoda,  etc.,  refer  to  the  foot,  one  of  the  most  stable 
molluscan  organs.1 

The  classification  adopted  in  this  guide  is,  with  certain 
modifications,  that  of  W.  H.  Ball2  and  of  Dr.  Robert  T. 
Jackson.  Dall  considers  the  structure  and  development 
of  the  hinge  first,  and  secondly,  the  sum  total  of  organic 
characters.  As  a  result  of  these  studies  he  divides  the 
class  into  three  orders.  The  first  possesses  the  simplest 
possible  hinge,  having  the  two  toothless  edges  of  the 
shell  in  contact  and  united  by  a  ligament.  The  second 
has  the  hinge  provided  with  transverse  or  cardinal  teeth 
and  the  third  has  teeth  parallel  with  the  margin  and 
known  as  lateral  teeth. 3  There  is  no  sharp  line  of  divi- 
sion between  the  last  two  orders,  as  many  shells  have  both 
the  cardinal  and  the  lateral  teeth.  In  these  cases  the 
general  characters  usually  enable  one  to  decide  to  which 
order  a  shell  belongs.  There  is  here  as  in  every  class 
the  difficulty  of  determining  the  primitive  and  the  reduced 
forms.  Some  shells  that  do  not  possess  teeth  to-day  are 
really  the  descendants  of  toothed  shell-bearing  Mollusca. 
On  the  other  hand  the  most  primitive  Pelecypods  were 
doubtless  toothless.  Whether  these  truly  primitive  forms 
exist  at  the  present  time  is  a  question.  Many  of  the 
members  of  Ball's  first  order  have  become  extremely 

1  Ball,  Amer.  Journ.  Sci.,  ser.  3,  XXXVIII,  1889,  p.  446. 

2  Rep.  on  Mollusca,  Bull.  Mus.  Comp.  Zool.,  XII,  1886;    Amer. 
Journ.  Sci.,  ser.  3,  XXXVIII,  1889,  p.  445  ;    Trans.  Wagner  Free 
Inst.  Sci.,  Phila.,  Ill,  part  3,  1895. 

3  See  Bernard,  Bull.  Soc.  Ge"ol.  de  France,  ser.  3,  XXIII,  1895  ; 
XXIV,  1896. 


198  SYNOPTIC    COLLECTION. 

specialized  through  the  habit  of  boring,  etc.,  so  that  it 
would  seem  as  if  these  were  reduced  rather  than  primi- 
tive forms  of  the  class.  It  is  probable,  however,  that  they 
are  simply  reduced  members  of  the  order  which  has  Sol- 
enomya  and  Anatina  for  its  primitive  representatives. 
The  weak,  toothless  condition  of  the  ancestors  could 
hardly  be  preserved  in  the  descendants,  as  pointed  out  by 
Dall,  unless  the  animals  became  borers  or  burrowers. 

If  the  shell-bearing  ancestral  form  of  the  Mollusca  is 
sought  in  the  Cambrian  formations,  one  finds  that  nearly 
four  hundred  species  of  molluscs  then  existed  which 
include  representatives  of  nearly  all  the  great  orders  exist- 
ing'to-day,  and  which,  according  to  Cooke,1  are  without 
the  slightest  sign  of  approximation  to  one  another.  If 
this  is  true,  the  point  of  convergence  of  these  divergent 
lines  lies  far  back  in  pre-Cambrian  times.  Until  more 
investigations  have  been  made  on  these  ancient  rocks, 
one  can  judge  of  the  ancestral  forms  of  Pelecypods  suc- 
ceeding the  plate  or  cap-like  condition  by  inference  only. 
It  seems  probable,  however,  that  such  a  form  possessed  a 
small,  smooth,  more  or  less  circular  shell ;  that  the  two 
valves  were  equal  in  size  and  were  connected  at  the  tooth- 
less hinge  area  by  a  flexible  membrane,  the  ligament. 
This  is  the  character  of  the  young  shell  or  prodissoconch 
(Jackson)  of  many  larval  bivalves  existing  to-day.  Such 
a  form  may  be  represented  by  Modioloides  prisca  Walcott 
(No.  369,  fig.  i,  enlarged),  found  as  an  internal  cast  in 
the  Cambrian  formation.  Another  genus,  Cardiola  (No. 
369,  fig.  2,  C.  cornucopiae  Goldf.),  possesses  most  of  the 
archetypal  characters. 

The  descendants  of  such  a  form  may  be  Solenomya, 
Anatina,  and  the  like.  Soknomya  velum  Say  (No.  370 ; 
No.  371,  shells),  has  a  small,  thin,  delicate  shell,  having, 
contrary  to  rule,  the  posterior  end  shorter  than  the  ante- 

1  Cambridge  Natural  History,  Til,  1895,  p.  2. 


METAZOA — MOLLUSCA.  199 

rior.1  A  glossy  horny  layer  covers  the  opening  between 
the  valves;  when  the  animal  is  young  (No.  371  a),  this 
horny  layer  is  entire  or  simply  pinked  at  the  anterior  and 
posterior  ends,  but  as  the  animal  grows  older  it  is  slit 
into  strips  (No.  371).  The  hinge  is  without  teeth.  The 
internal  portion  of  the  ligament  is  back  of  the  beaks  in  a 
triangular  receptacle  and  is  strengthened  by  limy,  arched 
supports.  Just  in  front  of  the  latter  are  the  distinct  ante- 
rior muscle  marks.  The  shell  of  most  primitive  forms  is 
nacreous,  that  is,  pearly,  but  Solenomya  is  only  slightly 
so.  The  gills  of  this  genus  are  in  a  primitive  condition, 
similar  to  those  of  Nucula  (see  p.  202).  The  foot  (No. 
370)  does  much  hard  work  enabling  the  animal  to  swim 
and  to  bore,  so  that  it  is  large  in  proportion  to  the  size  of 
the  animal.  The  mantle  is  not  drawn  out  into  tubes  or 
siphons. 

Anatina  truncata  Lam.  (No.  372),  is  a  delicate,  trans- 
lucent, and  pearly  shell  with  the  posterior  end  truncated 
and  the  anterior  rounded.  The  two  valves  are  open 
nearly  all  the  way  round,  so  that,  as  compared  with  many 
bivalves,  they  afford  slight  protection  to  the  soft  body 
within.  According  to  Smith2  one  species  of  this  genus, 
Anatina  elliptica,  shows  the  two  ends  nearly  alike,  while 
others  have  the  anterior  portion  longer  than  the  posterior, 
the  reverse  being  the  case  with  the  young. 

The  hinge  has  a  socket  for  the  internal  ligament  called  a 
fossette,  which  is  strengthened  in  its  position  by  two  limy 
supports  that  radiate  downward  towards  the  center  of  the 
shell  (No.  372,  specimen  at  right). 

This  genus  has  only  two  gills,  one  on  each  side  of  the  so 

1  When  we  speak  of  the  anterior  and  posterior  end  of  a  shell,  the 
latter  is  mounted  with  the  anterior  end  away  from  the  observer  — 
a  favorable  position  for  comparison  with  one's  own  body.     In  other 
cases  the  shells  are  mounted  to  show  certain  important  features. 
In  a  few  cases  delicate  shells  have  been  left  as  first  mounted,  owing 
to  the  danger  incurred  in  remounting. 

2  Chall.  Rep.,  Zool.,  XHI,  part  35,  1885,  p.  77. 


200  SYNOPTIC    COLLECTION. 

called  body.1  It  has  tubes  or  siphons  which  are  separate 
throughout  their  whole  extent,  and  a  foot  with  a  cleft. 

A  peculiar  bivalve  with  a  body  larger  than  its  shell  is 
illustrated  by  Cyrtodaria  siliqua  Daudin  (No.  373).  One 
preparation  shows  the  remarkably  large  muscular  siphon 
extended  at  the  posterior  end  and  the  comparatively  small 
foot  at  the  anterior  end.  The  other  preparation  is  the 
fleshy  animal  taken  from  its  shell.  The  plump,  rounded 
body  contains  most  of  the  internal  organs.  There  are 
two  gills,  one  on  either  side  of  the  body,  and  each  gill 
consists  of  two  leaves. 

Mya  arenctria  Linn.  (Pis.  374,  376;  No.  375),  is  one 
of  our  commonest  shells.  Ryder2  has  shown  that  the 
young  clam  is  attached  by  a  mass  of  threads  called  a 
byssus,  but  probably  only  for  a  short  time.  The  two 
valves  in  youth  and  maturity  are  equal,  therefore  the 
shell  is  equivalved  (PI.  374;  No.  375),  but  the  anterior 
end  is  broader  than  the  posterior  (PL  374).  The  light 
brown  external  horny  layer  is  thin  and  usually  worn  off, 
showing  the  lines  of  growth  which  are  the  edges  of  the 
layers  that  make  up  the  shell.  The  left  valve  (PI.  374, 
valve  on  the  left)  is  provided  with  one  tooth  (instead  of 
three  as  is  usually  the  c'ase),  and  the  right  valve  (PI.  374, 
valve  on  the  right)  with  a  cavity  which  contains  the  inter- 
nal ligament.  The  impressions  of  the  two  muscles,  the 
mantle,  and  the  siphon,  are  more  distinctly  seen  in  shells 
of  Mactra  (see  Nos.  411-413). 

The  clam  is  a  differentiated  member  of  its  order.  Since 
the  internal  organs  are  also  better  seen  in  the  larger  genus, 
Mactra,  we  will  speak  briefly  of  them  here.  The  mantle 
has  become  a  sac-like  organ  with  three  openings,  two  at 
the  end  of  the  siphon  and  one  at  the  anterior  end  through 
which  the  foot  passes.  The  mantle  is  thickened  on  the 
edge  and  supplied  with  pigment  cells  which  produce  many 
of  the  colors  of  the  shell. 

1  Bull.  Mus.  Comp.  Zool.,  XII,  1886,  p.  306. 
8  Amer.  Nat.,  XXIII,  1889,  p.  65. 


METAZOA MOLLUSCA.  201 

The  gills  have  become  more  complex,  consisting  of 
many  longitudinal  tubes  connected  by  cross  tubes. 

The  mouth  is  provided  with  two  pairs  of  palpi  and 
leads  into  the  so  called  "body"  containing  the  stomach, 
liver,  most  of  the  intestines,  and  the  reproductive  organs. 
The  long,  cartilaginous  rod  called  the  crystalline  style 
may  give  rigidity  to  this  part  of  the  animal.  The  intestine 
leaves  the  body,  passes  dorsally  under  the  beak  and 
through  the  heart.  It  terminates  a  short  distance  from 
the  upper  tube  of  the  siphon  lying  in  the  path  of  the  out- 
going current  of  water. 

The  more  specialized  members  of  the  group  are  Pholas, 
Aspergillum,  and  Teredo. 

Pholas  dactylus  (Nos.  377,  378)  has  a  large  opening  in 
the  anterior  end  filled  by  the  foot.  This  genus  has  the 
habit  of  boring.  The  valves  are  united  by  an  external 
ligament,  and  the  hinge  has  two  plates  to  strengthen  the 
union  but  no  teeth. 

Aspergillum  when  young  has  a  bivalve  shell.  As  the 
animal  grows  older  the  siphon  grows  to  a  large  size,  and 
is  covered  by  a  limy  tube  in  which  the  tiny  reduced 
bivalve  shell  becomes  imbedded,  as  seen  in  No.  379, 
specimen  at  the  right.  At  the  end  of  the  tube  is  a  sieve 
surrounded  by  a  frill.  At  the  other  end  are  one  or  more 
frills  which  are  broken  off  in  the  specimen.  In  Asper- 
gillum the  mantle  is  bag-like,  having  the  two  si  phonal 
openings  and  one  at  the  anterior  end. 

Teredo  has  a  long  body ;  at  the  larger  end  is  a  little 
bivalve  shell  which  is  without  teeth  or  ligament.  The 
mantle  is  drawn  out  into  a  long  siphon  near  the  end  of 
which  are  organs  probably  used  for  boring  into  wood.  It 
is  a  strange  freak  that  causes  the  animal  to  live  in  wood, 
since  it  never  uses  it  for  food.  Early  in  life,  however,  it 
begins  to  bore,  and  lines  its  tunnel  with  a  calcareous 
secretion  as  seen  in  No.  380.  It  never  leaves  its  tunnel 
and  depends  for  food  upon  the  microscopic  plants  and 
animals  which  are  brought  in  the  water.  Many  Teredos 


202  SYNOPTIC    COLLECTION. 

may  bore  into  the  same  piece  of  wood,  but  these  tunnels 
do  not,  as  a  rule,  come  in  contact. 

The  second  group  of  Pelecypods,  or  those  possessing 
transverse  teeth  on  the  hinge  area,  may  have  descended 
from  forms  like  Nucula  or  even  from  some  simpler  spe- 
cies.1 Nucula  occurs  in  the  ancient  formations  (No.  381, 
JV.  ventricosa  Hall)  and  has  continued  slightly  modified 
to  the  present  day  (No.  382,  N.  tenuis ;  No.  383,  N.  mar- 
garitacea  Lam.).  It  is  a  smooth,  symmetrical  shell  with 
equal  valves.  Contrary  to  the  usual  rule  the  umbos  are 
directed  towards  the  posterior  end  of  the  body  which  is 
short  and  rounded,  while  the  forward  end  is  longer  and 
more  pointed.  The  primitive  hinge  area  is  curved  and 
bears  a  few  teeth  which  are  at  right  angles  to  the  antero- 
posterior  axis  of  the  body.  This  primitive  hinge  area  or 
cardo  is  better  seen  in  the  larger  shell,  Area  Occident  alts 
Phil.  (No.  384).  Here  it  is  long  and  straight,  and  the 
many  transverse  teeth  are  well  developed.  In  this  genus 
the  umbos  are  widely  separated  and  the  ligament  lies 
between  them.  In  Nucula  the  hinge  area  has  a  triangular 
pit  for  the  internal  portion  of  the  ligament,  called  by 
Dall  the  "resilium,"  which  aids  the  external  ligament  in 
uniting  and  opening  the  valves.  The  whole  shell  is  made 
of  a  pearly  or  nacreous  substance,  and  in  its  young  and 
adult  stages  no  prismatic  structure  is  ever  developed. 
The  fleshy  animal  is  primitive  in  structure  like  its  shell. 
The  edges  of  the  mantle  are  free,  without  tentacles,  and 
are  not  drawn  out  to  form  a  tube  or  siphon.  Two  adduc- 
tor muscles  are  present,  one  at  either  end  of  the  body. 
The  gills  are  in  two  pairs  in  the  form  of  simple,  straight, 
and  separate  filaments.  The  young  Nucula  is  active  and 
throughout  life  it  never  becomes  attached.  The  foot  has 
a  cleft  and  can  be  flattened  into  a  disc  and  used  in 
crawling. 

1  For  a  discussion  of  the  subject  see  Verrill,  Trans.  Conn.  Acad. 
Arts  and  Sci.,  X,  part  i,  1899,  p.  45. 


METAZOA MOLLUSCA.  203 

Rhombopteria  (PI.  385)  represents  a  branch  from 
the  primitive  Nuculoid  ancestral  form,  and  is  the  probable 
ancestor  of  the  Aviculidae  to  which  Pecten  belongs.  Its 
shell  was  oblique,  and  it  had  a  straight  hinge  line  which 
extended  on  either  side  of  the  umbos. 

The  young  of  another  genus,  Pterinopecten,  resembles 
the  adult  Rhombopteria,  while  the  hinge  line  of  the  adult 
is  long  and  the  ears  slightly  developed.  The  young 
Aviculopecten  resembles  the  adult  Pterinopecten  but  the 
adult  has  a  shortened  hinge  line  and  a  much  greater 
development  of  the  ears. 

The  shell  of  the  young  Pecten  (PI.  386,  fig.  i,  viewed 
from  the  left  side;  fig.  2,  the  same  from  the  right  side; 
x  50  diameters)  has  the  embryonic  sheH  or  prodisso- 
conch  which  represents  the  ancestral  Nucula  while  the 
succeeding  stages  resemble  Rhombopteria,  Pterinopecten, 
and  Aviculopecten.  At  first  there  are  no  plications  and 
the  prodissoconch  is  without  ears.  According  to  Dall l 
the  very  young  valves  of  many  species  of  Pecten  have  the 
transverse  groovings  of  the  hinge,  representing  the  teeth 
of  Nucula  and  Area.  Fig.  3  is  an  older  stage,  x  40 
diameters,  and  fig.  4  shows  the  fleshy  animal  at  the  same 
stage.  The  two  mantle  borders  are  free  and  each  posses- 
ses a  single  row  of  eyes  which  alternate  with  single  ten- 
tacles. In  a  later  stage  two  tentacles  alternate  with  one 
eye.  The  animal  uses  its  long  narrow  foot  actively  so 
that  it  is  finely  developed.  Fig.  5  is  the  same  shell  viewed 
from  the  right  side,  while  fig.  6  is  an  older  shell,  x  16 
diameters.  The  plications  and  ears  are  now  well  devel- 
oped. The  two  borders  of  the  mantle  are  extended  to 
form  a  tube  just  under  the  dorsal  ear.  Here  the  effete 
matter  is  carried  away  in  the  outgoing  current  of  water, 
the  direction  of  the  current  being  indicated  by  an  arrow 
(fig.  6)  .  The  gills  of  the  very  young  Pecten  are  probably 
four  sets  or  two  pairs  of  straight  filaments,  but  when  the 

1  Amer.  Journ.  Sci.,  ser.  3,  XXXVIII,  1889,  p.  459. 


204  SYNOPTIC    COLLECTION. 

young  animal  has  reached  the  stage  represented  by  fig.  6 
the  ends  of  the  inner  pair  are  turned  inward  while  those 
of  the  outer  pair  are  reflected  outward,  as  seen  in  fig.  7 
which  represents  the  gills  of  the  adult.  When  young  the 
Pecten  attaches  itself  by  a  byssus  and  always  lies  on  the 
right  valve.  After  becoming  attached  it  may  detach  itself 
but  soon  becomes  fastened  again.  When  it  reaches  adult 
life  it  is  free,  but  keeps  the  same  position  with  the  right 
valve  below,  and  swims  by  clapping  its  valves  together. 
At  this  stage  the  hinge  is  toothless.  No.  387  is  a  species 
of  Pecten  showing  the  mantle,  large  muscle,  and  gills. 
Pecten  varius  Linn.  (No.  388),  illustrates  the  unequal 
development  of  the  ears  and  the  variation  in  color  in  one 
species.  No.  "389  is  a  remarkably  fine  specimen  of  the 
adult  Pecten  maximus,and  PI.  390,  figs,  i,  2,  are  drawings 
of  the  same.  Here  we  have  in  one  shell  an  epitome  of  a 
great  part  of  the  life  history  of  the  group  to  which  Pecten 
belongs. 

The  prodissoconch  has  disappeared,  the  peduncle  hav- 
ing usurped  its  place,  but  the  tiny  cavity  (No.  389 ;  PL 
390,  fig.  2)  at  the  beak  remains,  telling  of  the  rounded 
outline  and  long  hinge  line  of  the  embryonic  shell.  The 
larval  or  nepionic  stage  is  convex  at  first  and  smooth  with 
concentric  markings.  The  hinge  is  long,  while  ears  and 
ribs  are  not  developed.  In  the  later  nepionic  stage  the 
beginnings  of  ribs  are  seen.  At  this  time  the  shell  is 
light  yellow  in  color.  In  the  adolescent  or  neanic  stage 
the  shell  becomes  concave  and  ribs  are  more  developed. 
The  mature  or  ephebic  stage  is  convex  at  first  and  the 
ribs  are  prominent,  while  the  color  has  changed  to  red- 
dish. The  later  ephebic  stage  shows  a  tendency  to  return 
to  the  concave  condition  which  increases  in  the  gerontic 
stage.  This  is  seen  in  the  specimen  and  in  fig.  2,  but 
still  better  in  fig.  i,  which  is  a  section  through  the  middle 
of  the  two  valves,  the  lower  valve  being  on  the  right. 
The  ribs  tend  to  flatten  out  in  the  gerontic  stage,  while 
the  concentric  markings  become  prominent  and  are  nearer 
together. 


METAZOA MOLLUSCA.  205 

In  passing  through  these  stages  the  shell  illustrates 
Minot's  law  of  growth  ;  /'.  ^.,  growth  decreases  as  the  size 
of  the  animal  increases.  In  the  younger  stages  growth 
was  rapid,  the  hinge  extended  in  length  and  the  shell 
doubled  its  size  in  a  brief  time,  but  in  the  gerontic  stage, 
growth  is  limited  and  the  hinge  area  is  narrow,  as  seen 
by  tracing  the  edges  of  the  layers  from  the  broad,  rounded, 
posterior  part  to  the  comparatively  short  hinge  line. 

Anomia  (PI.  391,  A.  simplex,  No.  392),  is  related  to 
Pecten  though  it  is  a  much  more  specialized  form.  When 
young  it  is  found  free  and  crawls  by  means  of  its  large 
foot  which  is  seen  extended  in  PI.  391,  fig.  2.  The  very 
young  shell  (fig.  i,  left  or  upper  valve)  has  the  prodisso- 
conch  on  the  edge.  Fig.  2  is  a  somewhat  older  stage 
seen  from  the  left  or  upper  side.  The  later  dissoconch 
layers  of  shell  are  beginning  to  encircle  the  prodissoconch. 
Fig.  3  is  the  same  shell  as  Fig.  2  viewed  from  the  right 
or  lower  side.  The  byssal  notch  is  indicated  on  the  edge 
of  the  prodissoconch  in  which  particular,  Anomia  differs 
from  Pecten,  the  latter  having  an  entire  prodissoconch. 
The  byssal  notch  was  originally  on  the  edge,  but  has 
extended  nearly  to  the  center  and  is  partly  encircled  by 
the  layers.  The  prodissoconch  becomes  entirely  enclosed 
by  layers.  Fig.  4  is  an  older  stage  which  shows  how  the 
encircling  layers  have  pushed  the  prodissoconch  inward 
some  distance  from  its  original  position  on  the  margin. 

The  byssal  notch  of  the  lower  valve  is  finally  com- 
pletely enclosed  by  shell  layers,  as  seen  in  fig.  5  (adult 
Anomia,  lower  side  ;  fig.  6,  side  view  of  the  same). 

At  first,  when  the  byssus  is  surrounded,  the  opening 
or  foramen  is  small,  but  it  becomes  larger  by  the  resorp- 
tion  of  the  shell. 

Specimens  of  the  adult  are  seen  in  No.  392  ;  (a)  is 
the  whole  shell;  (b)  the  upper  valve  showing  the  scaly 
appearance  due  to  the  irregular  layers  of  shell ;  (c)  is  the 
lower  valve. 

The    same    trunk    forms,  Nucula    and    Rhombopteria, 


206  SYNOPTIC    COLLECTION. 

probably  gave  rise  to  Leptodesma  (PI.  393)  which  has  an 
oblique  body  with  the  posterior  wing  extended,  while  the 
anterior  border  is  acute  and  there  is  a  byssal  sinus. 
These  forms  may  in  time  have  produced  another  series 
represented  by  Aviculopinna  and  Pinna. 

Aviculopinna  (PI.  394)  is  wedge-shaped  and  without 
ears.  The  two  valves  are  equal  and  marked  by  concen- 
tric lines.  The  beaks  are  a  little  behind  the  anterior  end 
of  the  shell. 

Pinna  (No.  395,  P.  rudis  Linn.),  the  probable  descend- 
ant of  Aviculopinna,  has  the  same  wedge-shaped,  equi- 
valved,  and  earless  shell.  The  concentric  and  longitudinal 
markings  are  about  equally  developed.  The  beaks  in 
Pinna  are  placed  at  the  anterior  end  of  the  shell.  The 
hinge  is  in  a  reduced  condition,  having  no  teeth,  and  the 
substance  of  the  shell  is  mostly  prismatic,  very  little 
nacreous  matter  being  found. 

In  this  form  the  anterior  muscle  is  four  or  five  times 
smaller  than  the  posterior,  being  on  the  way  to  a  reduced 
condition.1 

Other  descendants  of  Nucula,  Rhombopteria,  and 
Leptodesma  were  probably  Melina,  Avicula,  (=  Pteria) 
Malleus,  and  Ostrea. 

The  shell  of  Melina  (No.  396;  PL  397,  figs,  i,  2)  is 
extremely  flat,  and  the  posterior  part  is  prolonged  to  one 
side  making  .the  shell  appear  as  if  deformed.  The  hinge 
area  (PL  397,  fig.  2)  has  little  pits  for  the  ligament  which 
holds  the  two  valves  together. 

Avicula^  (PL  398,  fig.  i,  young),  has  the  Nucula-like 
prodissoconch  and  the  subsequent  nepionic  stage  repre- 
senting Rhombopteria.  It  has  a  straight  hinge  line,  but 
its  posterior  wing  is  extended  and  there  is  a  deep  byssal 
sinus  in  the  right  valve  (fig.  2).  The  triangular  pit  exists 
in  all  Aviculas.  The  later  stage  represented  by  fig.  3  is 
the  Leptodesma  stage.  The  adult  has  the  shell  oblique 

1  Sharp,  Proc.  Acad.  Nat.  Sci.,  Phila.,  1888,  pp.  122,  123. 


METAZOA MOLLUSCA.  207 

and  the  right  valve  is  smaller  and  flatter  than  the  left. 
The  hinge  has  one  or  two  transverse  or  cardinal  teeth. 

Malleus  when  young  (No.  399  a)  somewhat  resembles 
the  adult  Avicula.  The  hinge  line  is  long  with  the  beak 
at  one  end.  Only  one  wing  is  developed.  Later  growth 
takes  place  on  the  other  side  of  the  beak  (No.  ^gb)  and 
the  result  is  a  wing  in  masquerade.  The  adult  (No.  400) 
for  obvious  reasons  is  familiarly  known  as  the  "hammer- 
oyster." 

One  of  the  ancestral  forms  of  the  oyster  was  Gryphaea 
arcuata  Lam.  (No.  401).  The  large  deep  lower  valve  and 
the  small  lid-like  upper  valve,  the  curved  beak  and  the 
lines  of  growth  are  all  well  preserved  in  the  fossil. 

The  development  of  the  oyster  from  the  embryo  to  the 
adult  is  given  in  PI.  402,  figs.  1-19  ;  figs.  1-3,  Ostrea 
edu Us  \Jx\n.\  figs.  4-19,  our  common  species,  O.  virgin- 
tana  Listner  (=O.  virginica  Gmel.).  The  segmentation 
and  earliest  embryonic  stages  are  omitted,  although  like 
the  later  stages,  they  illustrate  accelerated  development. 
In  the  embryonic  stage  (figs.  1-3)  the  shell  is  symmet 
rical  with  a  straight  hinge  line  (fig.  i)  situated  on  the 
dorsal  side.  The  valves  are  equal  (fig.  2)  with  only 
slightly  developed  umbos.  In  this  condition  the  shell 
bears  a  striking  resemblance  to  the  equivalved  bivalves 
already  described. 

At  this  time  both  the  mouth  (fig.  3,  m)  and  anus  (fig.  3, 
a)  are  situated  ventrally,  while  there  is  but  a  single 
muscle,  the  anterior  adductor  (fig.  3,  a,  a) .  A  ciliated 
velum  (fig.  3,  v)  still  persists  as  the  little  oyster  swims 
about  freely  in  the  sea. 

The  stages  of  development  between  the  one  repre- 
sented by  figs.  1-3  and  that  shown  by  figs.  4,  5,  have 
never  been  figured  or  described.  The  latter  (figs.  4,  5) 
represents  our  common  species,  when  it  has  completed  the 
embryonic  or  prodissoconch  stage,  and  has  fastened  itself 
by  the  edge  of  the  left  valve  (fig.  5),  using  the  reflected 
margin  of  the  mantle  (fig.  5,  m)  to  accomplish  the  work. 


208  SYNOPTIC    COLLECTION. 

This  early  fixation  of  the  oyster  has  doubtless  caused  the 
reduction  of  the  foot,  which  exists  as  a  mere  vestige  in  an 
early  embryonic  stage  and  is  lost  altogether  before  the 
embryonic  stages  figured  in  PL  402. 

The  straight  hinge  line  of  the  embryonic  shell  has 
given  way  to  a  curved  line  with  high  umbos  (figs.  4,  5  ; 
also  fig.  6,  which  shows  the  shell  attached  by  the  left 
valve  in  an  almost  vertical  position).  An  important 
change  has  taken  place  in  the  structure  of  the  oyster,  for 
instead  of  having  one  muscle  it  now  possesses  two,  a 
posterior  adductor  (figs.  4,  5,/tf)  having  been  developed. 

The  gills  (figs.  4,  5,  g)  are  still  in  a  primitive  condition, 
consisting  of  straight  simple  filaments  (fig.  7).  The  sit- 
uation of  the  mouth  can  be  judged  by  the  position  of  the 
palpi  (figs.  4,  5,//),  but  the  anus  has  changed  its  place, 
having  moved  dorsally  before  the  development  of  the 
posterior  adductor  muscle  which  took  place  on  its  ventral 
side. 

The  beginning  of  the  nepionic  stage  is  represented  in 
fig.  8.  Here  the  left  valve  is  below  and  the  right  above, 
and  on  the  edges  of  these  valves  the  new  growth  of  the 
nepionic  shell  is  being  added  to  the  prodissoconch.  The 
internal  organs  in  the  early  nepionic  stage  are  shown  in 
fig.  9.  The  single  adductor  muscle  (fig.  9,  ad)  is  in  a 
similar  position  to  that  of  the  adult.  The  gills  have 
passed  througn  the  stage  represented  by  fig.  10  and  are 
now  in  the  condition  illustrated  by  fig.  n,  in  which  the 
filaments  are  connected  by  cross  bars. 

The  substages  of  the  nepionic  stage  are  so  well  shown 
in  the  shell  of  the  oyster,  that  contrary  to  our  usual  rule, 
we  illustrate  them  by  figures.  Fig.  12,  /,  represents  the 
prodissoconch  succeeded  by  the  first  nepionic  growth. 
In  figs.  13  and  14  two  and  a  half  of  the  third  nepionic 
substages  are  figured.  At  this  time  the  right  or  upper 
valve  is  convex  (fig.  13)  and  the  left  or  lower  valve  (fig.  14) 
is  flat.  The  tip  of  the  left  valve  (fig.  15,  x  87  diameters, 
view  of  interior)  shows  the  prodissoconch  (fig.  15,  /) 


METAZOA —  MOLLUSCA.  209 

and  the  nepionic  growth  with  the  cartilage  pit  or  furrow 
running  through  the  middle.  On  either  side  of  the  true 
nepionic  shell  there  is  a  flange-like  extension  (fig.  i5,/) 
of  the  margin  which  passes  over  the  object  of  support. 

The  shell,  as  it  appears  at  the  end  of  the  four  nepionic 
substages  and  the  neanic  stage,  is  represented  in  fig.  16, 
right  valve,  and  fig.  17,  left  valve.  The  sinus  (figs.  16,  17, 
s)  is  clearly  indicated,  and  it  marks  the  position  of  the 
outgoing  current  of  water.  Changes  take  place  in  the 
shape  of  the  shell  during  the  ephebic  stage,  the  variations 
depending  largely  upon  the  surroundings.  As  a  rule  the 
lower  or  left  valve  becomes  deep  and  cup-shaped,  while 
the  right  valve  flattens.  This  is  seen  in  fig.  18,  which 
represents  two  adults.  The  upper  specimen  is  growing 
with  the  left,  deep  valve  below,  and  the  right,  flat  valve 
above.  The  right  hand  specimen,  however,  reverses  this 
condition,  so  that  the  left,  deep,  attached  valve  is  above 
and  the  flat  valve  below.  In  both  cases  the  same  relative 
form  of  the  valves  is  maintained. 

The  adult  oyster  (No.  403,  alcoholic  specimen  ;  404, 
model;  405,  shells,  young  and  adult)  has  but  one  muscle, 
the  anterior  adductor  having  disappeared.  The  posterior 
adductor  holds  a  more  central  position  (Nos.  403,  404) 
and  the  dark  purple  scar  is  seen  in  No.  405.  The  palpi 
have  moved  dorsally  and  are  nearer  the  hinge  line.  The 
model  shows  the  two  leaves  of  the  mantle,  one  of  which 
is  thrown  back  exposing  the  gills.  These  organs  have 
become  more  complicated  in  structure,  as  shown  by  PI. 
402,  fig.  19. 

Unionidae.  It  is  very  rare  to  find  parasites  at  any 
period  of  life  among  molluscs.  The  fresh-water  Lamp- 
silis  (=  Unio)  (No.  406,  Z.  nasutus  Say;  Nos.  407,  408, 
L.  radiata  Gmel.)  and  Anodonta  (No.  409)  however, 
pass  the  young  stage  attached  to  fishes.  Their  develop- 
ment is,  therefore,  more  complicated  than  that  of  most 
molluscs.  The  eggs  are  carried  in  little  pouches  in  the 
gill  cavities  of  the  parents.  No.  407  is  the  female  of 


210  SYNOPTIC    COLLECTION. 

Lampsilis  radiata  with  the  broad  sacs  of  the  outer  gills 
filled  with  embryos. 

The  peculiar  characters  which  separate  the  larvae  of 
the  Unionidae  from  those  of  other  Pelecypods  appear 
very  early  in  the  embryo  and  are  found  in  both  the  inter- 
nal and  the  external  parts.  A  shell  is  formed  with  a 
straight  hinge  line.  It  is  provided  with  hooks  which  later 
become  a  necessity  to  the  larvae.  The  byssus  and  spiny 
beaks  form,  and  peculiar  sense  organs  are  developed  on 
the  inner  surface  of  the  mantle.  All  this  takes  place 
before  the  animal  leaves  its  parent.  This  stage  is  known 
as  the  glochidium.  Becoming  free,  the  glochidium 
attaches  itself  by  the  byssus,  or  if  fish  are  near  it,  fastens 
itself  to  the  gills,  fins,  or  other  parts  of  the  fish  by  the 
hooks  of  its  shell  and  lives  the  life  of  a  parasite,  its  host 
providing  the  necessary  nourishment.  All  this  time  the 
intestine  is  a  closed  internal  sac  and  of  little  use.  Later 
the  sac  elongates  and  an  opening  breaks  through.  A 
metamorphosis  takes  place,  two  adductors  appear  in  place 
of  one,  gills  develop,  and  the  peculiar  sense  organs  disap- 
pear. When  fully  developed,  with  the  exception  of  the 
reproductive  organs,  it  leaves  the  fish  and  becomes 
extremely  lively  while  its  further  development  goes  on. 
The  adult  shell  (No.  406,  Lampsilis  nasutus  Say  ;  No.  407, 
L.  radiata  Gmel.) ,  has  the  transverse  teeth  which  prove 
the  origin  of  the  Unionida'e,  while  the  peculiar  marginal 
teeth  of  the  third  group  are  developed  later.  The  hinge 
of  Anodonta  (No.  409),  however,  is  so  much  reduced  that 
it  is  toothless. 

The  third  order,  in  which  there  are  teeth  parallel  to  the 
margin,  is  represented  by  a  number  of  genera.  It  is 
important  to  bear  in  mind  that  transverse  teeth  also 
usually  occur,  so  that  in  the  differentiated  forms  the  hinge 
is  remarkable  for  its  perfection  of  mechanism  for  efficient 
work. 

Petricola  is  both  a  free  and  a  boring  mollusc.  It  is 
found  in  soft  marshy  earth  as  at  Revere  Beach  and  also 


-    METAZOA — MOLLUSCA.  211 

in  limestone  rocks  (No.  410,  P.  corditoides).  The  teeth  of 
the  hinge  are  usually  broken  off,  but  when  preserved  there 
are  two  in  each  valve.  The  mantle  lobes  are  united. 
The  anterior  end  is  short  and  the  posterior  gaping. 

Mactra  (=  Spisula)  solidissima  Dillw.  (No.  411),  is 
one  of  our  largest  New  England  bivalves.  The  animal  is 
free-moving  and  is  therefore  symmetrical.  The  horny 
layer  is  light  brown  in  color  (Nos.  411,  412).  The  umbos 
are  directed  anteriorly.  The  pit,  with  its  internal  liga- 
ment, and  the  external  ligament  are  sometimes  developed. 
The  cardinal  tooth  is  nearly  vertical  while  the  marginal 
teeth  are  long.  The  dissection  (No.  413)  and  model 
(No.  412)  show  the  principal  internal  organs  and  give 
their  names.  The  mantle  is  seen  extending  along  the 
edge  of  the  shell  (Nos.  412,  413)  ;  it  has  three  openings; 
one  at  the  anterior  end  through  which  the  foot  passes  out, 
and  two  at  the  end  of  the  siphon.  This  siphon  is  really 
a  double  tube;  one,  "the  branchial  siphon,"  is  for  the 
ingoing  current  of  water,  and  the  other,  "the  cloacal 
siphon,"  for  the  outgoing  current.  The  anterior  and 
posterior  adductor  muscles,  the  gills  injected  with  red 
coloring  fluid,  the  mouth  organs  called  palpi,  and  the 
strong  muscular  foot  are  all  shown  in  the  preparation. 

Psammobia  vespertina  Gmel.  (No.  414),  has  two  long 
delicate  siphonal  tubes  separate  throughout  their  whole 
length.  The  siphonal  tubes  are  separate  only  a  short 
distance  in  Psammosolen  strigillatus  Linn.  (No.  415). 
The  foot  in  this  genus  is  of  great  size  and  strength. 

Ensis  directus  Con.  {Ensis  americana  Verr.)  (Nos.  416— 
418),  and  the  European  species,  Ensis  ensis  Linn.  (No. 
419)  have  a  long  razor-like  shell  covered  when  young  (No. 
416)  with  a  glossy  horny  layer,  but  which  is  often  partly 
worn  off  in  the  adult  (No.  417).  This  animal  travels 
rapidly  through  the  sand  as  can  be  proved  by  any  one 
who  attempts  to  dig  it  up.  Notwithstanding  this  fact,  the 
horny  layer  is  seldom  found  entirely  worn  off.  The 
model  (No.  418)  shows  the  adult  animal  with  the  mantle 


212  SYNOPTIC    COLLECTION. 

extended  from  the  shell;  at  one  end  is  the  siphon  and  at 
the  other  the  foot  (Nos.  417,  418). 

Donax  scortum  Linn.  (No.  420),  is  triangular  in  shape. 
The  hinge  area  has  two  cardinal  teeth  on  one  valve  and 
one  on  the  other  that  fits  between  the  two.  The  two 
marginal  teeth  fit  into  depressions.  A  rounded  ligament 
is  external. 

Cardium  edule  Linn.  (No.  421),  is  represented  by  shells 
of  different  ages.  At  first  the  shell  has  shallow  grooves 
or  plications,  but  these  grow  deeper  and  cause  the  shell 
to  be  thicker  and  stronger.  The  hinge  has  both  tranverse 
and  parallel  teeth.  The  umbos  are  close  together  and  the 
ligament  is  external.  The  muscle  impressions  are  distinct, 
but  the  mantle  mark  is  often  obscure,  while  there  is  no 
siphon  impression,  although  the  animal  has  a  short  siphon. 
In  Cardium  the  foot  (No.  422,  C.  aculeatuni)  can  be 
suddenly  bent  so  that  the  animal  leaps  through  the  water. 

The  changes  in  color  of  the  external  horny  layer  are 
finely  illustrated  by  Cyprina  islandica  Lam.  The  young 
(Nos.  423,  424)  is  light  brown  in  color.  This  becomes 
a  rich  shade  of  brown  in  the  adult,  while  in  the  old  shell 
(No.  424,  specimen  at  the  right)  it  is  nearly  black,  and  so 
brittle  that  it  can  be  easily  scraped  off  (No.  424).  The 
ligament  is  partly  internal  and  the  hinge  has  three  cardi- 
nal teeth  besides  the  marginal  teeth.  The  two  muscle 
impressions  and  the  mantle  impression  in  this  shell  are 
often  distinct  but  the  short  siphon  makes  no  mark. 

Cytherea  (=  Venus)  verrucosa  Linn.  (No.  425),  is  a  large 
plump  shell  when  full  grown  with  prominent  beaks,  be- 
hind which  is  a  large  external  ligament.  The  well  devel- 
oped hinge  area  has  three  cardinal  teeth.  The  shell  is 
porcellanous  like  most  of  the  more  specialized  shells,  with 
both  muscle,  mantle,  and  siphon  marks  well  shown. 
Smith  says1  that  one  species  of  this  genus  (C.  torresiand] 
has  the  posterior  end  broader  in  the  early  stages  than 

1  Chall.  Rep.,  Zool ,  XIII,  part  35,  1885,  p.  119. 


METAZOA MOLLUSCA.  213 

the  anterior  end,  while  in  the  adult  it  is  narrower.  This 
indicates  a  development  of  the  forward  or  head  end  of 
the  body. 

Hysteroconcha  lupanaria  Less.  (No.  426),  is  instructive 
as  showing  how  age  affects  the  development  and  increase 
of  spines,  ridges,  and  projecting  shelves.  The  young 
shell  is  smooth.  In  the  nepionic  stage  the  spines  are 
short.  They  appear  to  be  formed  by  the  shell  layers 
meeting  along  two  ridges  on  the  posterior  end  and  being 
prolonged  in  such  a  way  as  to  leave  a  groove  on  the 
upper  side  of  the  long  tapering  spine ;  in  these  grooves 
foreign  particles  are  often  caught. 

A  unique  specialization  of  the  Pelecypods  is  found 
in  the  Cretaceous  Coralliochama  (No.  427,  C.  orcutti 
White),  and  Radiolites  (PL  428).  In  Coralliochama 
one  valve  is  deep  and  more  or  less  distorted,  while  the 
upper  valve  is  convex  (see  No.  427).  In  Radiolites  the 
upper  valve  is  flat  and  serves  as  a  lid  or  cover.  These 
Pelecypods  may  be  related  to  the  Chamidae. 

Specialization  has  gone  on  in  Tridacna  crocea  Lam. 
(No.  429).  As  the  circular  young  shell  grows  older,  the 
wavy  lines  become  ridges  and  the  shell  lengthens  in  an 
antero-posterior  direction.  This  species  in  the  adult 
stage  is  colossal  in  size  and  all  traces  of  the  young  shell 
are  lost.  The  same  tendency  is  observed  in  Chama  laza- 
rus  Linn.  (No.  430)  where  the  originally  smooth  shell 
quickly  becomes  ornamented,  the  edges  of  the  layers  of 
shell  extending  into  short,  broad,  flat  spines. 


Sections.  —  GASTROPODA. 

The  earliest  larval  stage  of  existing  Gastropods  is  the 
trochophore  which  is  so  strikingly  like  the  trochophqre 
of  Pelecypods  already  described  that  the  two  probably 
arose  from  a  common  ancestor.  As  a  rule  the  tiny  cap- 
like  shell  of  the  Gastropod  becomes  a  cone,  as  seen  in 


214  SYNOPTIC    COLLECTION. 

PI.  431.  This  stage  succeeds  the  trochophore,  and  is 
known  as  the  veliger — a  characteristic  stage  in  the  devel- 
opment of  Gastropods.  The  ciliated  velum  still  exists 
and  the  foot  is  also  formed. 

In  most  Gastropods  this  cone-like  shell  becomes  a 
spiral,  but  in  Chitons  (No.  432,  C.  magnificus  Desh.), 
which  may  be  primitive  Gastropods,1  the  one-valved  shell 
is  made  of  eight  pieces.  In  No.  433  these  pieces  are 
separated  and  are  seen  to  be  essentially  alike. 

Chiton  existed  in  the  Silurian  age  and  has  undergone 
comparatively  little  change  since  that  time.  The  animal 
agrees  with  many  Pelecypods  in  being  bilaterally  symmet- 
rical. On  the  other  hand,  the  head  is  indistinctly 
marked  off  from  the  rest  of  the  body  and  there  is  a  well 
developed  lingual  ribbon  (an  apparatus  for  eating)  which 
is  possessed  by  Gastropods. 

The  cone-like  shell  may  be  represented  by  Tryblidium 
(PI.  434,  T.  nycteis  Billings)  from  the  Cambrian,  which 
had  a  smooth  cap-like  shell  when  young  with  an  entire 
margin,  becoming  in  the  adult  like  a  shallow  cone  (PI. 
434,  fig.  i)  with  the  apex  placed  near  the  forward  end 

(%•    2)- 

As  we  have  just  said,  the  cone  of  most  young  Gastro- 
pods becomes  a  spiral  and  this  youngest  spiral  shell  or 
protoconch  (PI.  43 5 )2  is  smooth,  rounded,  and  light  col- 
ored. It  is  formed  at  the  apex  of  the  shell  but  is  usu- 
ally broken  off  and  lost. 

In  the  Ordovician  fauna,   Pleurotomaria  (No.  436,  P. 


1  Conflicting  views  are  held  in  regard  to  the  position  of  the  Chi- 
tons.    Some  naturalists  place  them  before  the  Pelecypods,  while 
others  assign  them  a  position  between  the  Pelecypods  and  Gastro- 
pods.    They  are  here  placed  provisionally  among  the  more  primi- 
tive Gastropods. 

2  Although  this  is  the  protoconch  of  Fulgur,  (see  p.  223  and  Nos. 
462-465),  a  more  specialized  species  than  those  we  are  now  describ- 
ing, yet  it  is  placed  here  for  the  purpose  of  showing  the  general 
characters  of  the  Gastropod  protoconch. 


METAZOA MOLLUSCA.  215 

sulcomarginata)  occurs,  which  was  a  coiled  shell  consist- 
ing of  a  few  whorls  with  a  slit  in  the  margin  of  the 
aperture,  that  was  either  filled  as  the  animal  grew  older, 
making  a  continuous  band,  or  partly  filled  giving  rise  to 
openings. 

In  the  Silurian  and  Devonian  ages,  Platyceras  (No.  437, 
P.  erectum  Hall)  existed,  the  apex  of  which  was  twisted 
so  as  to  form  a  spiral  while  the  later  whorl  was  flaring, 
showing  a  tendency  to  uncoil.  —  an  old  age  or  gerontic 
character. 

In  the  group  of  Gastropods  represented  by  Tryblidium, 
Pleurotomaria,  and  their  descendants  Patella,  Haliotis, 
etc.,  there  seems  not  to  be  any  primitive  genus  with  a 
cap-like  shell  in  the  adult  stage.  Neither  is  there  a  genus 
with  the  loosely-coiled  shell,  the  transitional  form  between 
the  cap  and  the  close  spiral,  such  as  is  found  in  the  class 
of  Cephalopoda. 

Both  Patella  and  Fissurella  were  formerly  supposed  to 
be  primitive  members  of  the  group  to  which  they  belong; 
but  in  reality  they  are  found  to  be  specialized  forms. 
This  is  proved  by  their  development,  which  in  the  case 
of  Fissurella  has  been  figured  and  described  from  the  egg 
to  the  adult  stage.1 

Since  the  adult  Patella  is  less  modified  than  the  adult 
Fissurella,  it  will  be  briefly  described. 

We  pass  over  the  development  of  the  egg  and  the  for- 
mation of  the  embryonic  nautiloid  shell  figured  by  Patten,2 
and  come  to  the  patelliform  stages  of  the  shell.  In  one 
of  the  simplest  Patellidae,  Acmaea,  the  shell  is  without 
ribs,  spines,  or  ornaments  of  any  kind,  and  one  species, 
A.  punctulata  Gmel.,  is  conical  when  young  though  it  is 
depressed  like  most  of  its  group  when  full  grown. 

In  Helcioniscus  exaratus  Nutt.,  often  called  Patella 
(No.  438),  the  perfect  shell  is  smooth  at  the  apex,  but 

1  Boutan,  Arch,  de  Zool.  Exper.  et  Gdn.,  ser.  2,  III,  suppl.,  1885. 

2  Arbeit,  zool.  Inst.  Univ.  Wien,  VI,  1886. 


216  SYNOPTIC    COLLECTION. 

later  becomes  ribbed  or  crenulated.  In  all  the  shells  the 
margin  is  entire.  The  adult  of  Helcioniscus  has  a  circu- 
lar foot,  and  the  functional  lamellar  gills  which  are  called 
pallial  gills  lie  in  a  groove  between  the  foot  and  the  man- 
tle. These  are  really  secondary  gills,  as  the  original 
breathing  organs  exist  as  mere  remnants  on  each  side  of 
the  neck.  The  heart  of  Helcioniscus  consists  of  a  single 
auricle  and  ventricle. 

The  eggs  of  Fissurella  (PL  439,  figs.  1-12)  are  joined 
together  by  an  albuminous  substance  which  swells  in 
water  to  a  large  size,  like  that  in  which  frogs'  eggs  are 
embedded.  These  eggs  (fig.  i)  are  not  laid  through  the 
apical  hole,  as  has  been  supposed,  but  through  the  ante- 
rior opening  of  the  branchial  chamber.  The  egg  passes 
through  the  usual  stages  of  segmentation  until  the  embryo 
(fig.  2)  with  velum,  beginning  of  foot,  primitive  mouth, 
and  invaginated  shell  gland  is  attained. 

While  the  embryo  is  still  within  the  egg,  the  shell  is 
formed  (fig.  2).  At  first  it  is  made  of  particles  of  lime 
separated  from  each  other;  afterwards  these  become  con- 
solidated, and  the  shell  exhibits  a  lace-like  pattern.  Since 
the  characteristic  twisting  of  the  embryo  has  already 
begun,  the  shell  is  asymmetrical,  and  the  little  embryo 
has  the  characters  of  a  young  Gastropod,  i.  e.,  a  coiled 
shell,  a  ciliated  velum,  and  a  foot  (figs.  3,  4).  When 
still  older,  the  shell  possesses  an  operculum  (fig.  5). 

When  the  embryo  leaves  the  egg,  the  last  vestiges  of 
the  velum  remain  and  aid  the  foot  in  locomotion.  The 
embryonic  shell  is  not  replaced  by  another  but  is  persis- 
tent. Its  margin  begins  to  spread  out,  and  the  new 
layers  take  on  markings  very  different  from  the  plain 
embryonic  shell  (fig.  6,  dorsal  view;  fig.  7,  ventral  side). 
At  this  time  the  foot  is  long  and  narrow,  and  the  long 
tentacles  have  eyes  at  their  bases.  Up  to  this  time  the 
margin  has  been  entire,  like  the  margin  of  Patella,  but 
soon  a  slit  appears  (fig.  8).  Gradually  this  slit  is  sur- 
rounded by  shell  layers  whereby  it  is  converted  into  a 


METAZO  A  —  MOLLUSCA.  217 

hole,  while  the  coil  portion  of  the  shell  becomes  reduced 
in  size  and  is  carried  towards  the  posterior  end  (fig.  9). 
This  is  seen  on  the  edge  of  fig.  10,  which  is  a  ventral 
view  showing  the  foot,  eyes,  radula,  and  mantle.  With 
the  growth  of  the  shell  the  hole  approaches  the  summit 
(fig.  u),  until  finally  it  occupies  a  nearly  central  position 
with  the  vestige  of  the  coiled  shell  behind  it  (fig.  12). 
Thus  it  is  seen  that  the  symmetry  of  the  adult  (fig.  12  ; 
see  also  No.  440)  is  not  primitive  but  is  secondarily 
acquired. 

A  fold  of  the  mantle  lies  in  the  slit,  and  later  occupies 
the  hole.  It  is  thought  to  have  an  excretory  function, 
and  if  so,  it  serves  as  an  anal  siphon.  Fissurella  has  the 
original  gills  fully  developed,  one  on  each  side  of  the 
neck.  The  nephridia  are  also  present.  The  heart  has 
two  auricles  and  a  ventricle. 

Some  specimens  of  the  Stomatellidae  are  limpet-like, 
while  others  (No.  441,  Stomatella  imbricata  Lam.),  have  a 
spiral  shell  without  perforations  and  with  a  large  aperture. 

The  young  Haliotis  has  an  imperforate  shell,  but  in 
the  course  of  development  a  slit  occurs  in  the  margin 
of  the  aperture  through  which  the  siphon  is  extended. 
With  the  growth  of  the  shell  this  slit  is  not  continuous 
but  a  series  of  holes  is  formed  (see  Nos.  442,  443)  some 
of  which,  according  to  Cooke,  admit  water  to  the  gills, 
while  others  are  anal  in  function.  With  the  growth  of 
the  animal  the  first  formed  holes  tend  to  become  filled 
with  a  limy  deposit.  The  primitive  gills  and  excretory 
organs  or  nephridia  are  in  pairs  although  the  beginning 
of  the  spiral  has  brought  the  anus  from  the  posterior  end 
of  the  body  towards  the  anterior  median  line. 

The  specimen  of  Crucibulum  (No.  444,  C.  striatnm 
Say),  exhibits  the  fleshy  body  in  the  shell  with  its  mantle 
and  muscular  foot.  The  anterior  part  of  the  body  has 
become  differentiated  to  form  a  head  (see  No.  444)  which 
be.ars  sense  organs.  This  specialization  of  the  Gastro- 
pods in  general  shows  a  marked  advance  over  all  the 
classes  of  animals  so  far  described. 


218  SYNOPTIC    COLLECTION. 

The  shell  of  Crepidula  (No.  445,  C.  nivea  C.  B.  Adams), 
is  slightly  coiled  and  the  last  whorl  is  large  and  flaring 
like  that  of  Haliotis.  In  the  inside  a  projecting  horizon- 
tal wall  covers  the  posterior  half  of  the  shell.  No.  446 
shows  the  peculiar  habit  these  animals  possess  of  growing 
on  top  of  one  another.  Sometimes  one  species  of  Cre- 
pidula (C.  plana  Say)  takes  possession  of  the  inner  side 
of  a  univalve  shell,  often  Lunatia  heros  (No.  446).  Five 
or  six  different  stages  are  seen  in  this  specimen.  The 
young  shells  are  round  and  smooth,  as  compared  with  the 
adults,  which  are  long,  narrow,  and  extremely  flat.  Owing 
probably  to  the  hidden  situation  in  which  they  live,  they 
are  nearly  colorless. 

The  gills  in  the  family  Calyptraeidae,  to  which  Crepi- 
dula belongs,  are  much  more  like  Pelecypod  gills  than  are 
those  of  most  Gastropods.  The  lamellae  are  long  and 
much  like  filaments  and  are  strengthened  by  chitinous 
rods.1 

Since  the  primitive  or  embryonic  shell  is  uncoiled  and 
imperforate,  and  in  shape  like  a  cap  or  the  beginning  of 
a  cone,  we  know  that  the  spiral  condition  is  a  secondary 
one.  It  would  seem  most  probable  that  before  the  perfect 
spiral  form  was  attained  the  cone  would  be  loosely  coiled, 
arid  that  only  after  many  generations  and  a  long  period 
of  time  could  we  have  the  complete  amalgamation  of  the 
inner  wall  of  a  whorl  to  the  preceding  whorl  which  marks 
the  tightly  coiled  spirals  of  many  existing  species.  Since, 
also,  the  primitive  shell  is  usually  both  smooth  and  color- 
less or  nearly  so,  it  follows  that  the  highly  ornamented 
and  brilliantly  colored  shells  are  far  removed  from  the 
primitive  form.  The  ontogeny  of  many  Gastropods  has 
not  been  worked  out,  so  that  it  is  impossible  to  give  a 
classification  which  shall  show  the  genetic  relationships 
of  all  the  different  species.  It  is  most  probable  that  the 
ancestral  form,  represented  by  the  embryonic  shell  of 

1  Dall,  Bull.  Mus.  Comp.  Zool.,  XVIII,  1889,  p.  285. 


METAZOA MOLLUSCA.  219 

many  existing  species,  gave  rise  to  different  branches, 
each  one  of  which  has  passed  or  is  passing  through  a 
straight,  a  loosely  coiled,  and  a  tightly  coiled  stage.  In 
such  a  case  we  should  have  many  similar  forms  which  are 
not  closely  related  genetically  but  which  are  examples  of 
parallelism.  In  a  natural  classification  these  hold  their 
rightful  position  between  the  primitive  and  the  more 
specialized  members  of  their  respective  groups. 

Such  a  classification  is  not  based  upon  the  structure  of 
the  shell  exclusively,  inasmuch  as  the  shell  is  a  tell-tale  part 
of  the  organism  ;  generally  speaking,  a  straight  shell  has 
a  straight  body  within  it,  and  a  coiled  shell  a  coiled  body. 
The  straight  body  has  the  bilateral  symmetry  character- 
istic of  early  stages  of  animals,  while  the  coiled  body  has 
succeeded  in  making  such  a  twist  in  its  organs  as  to  bring 
the  opening  of  the  alimentary  canal  at  the  anterior  instead 
of  the  posterior  end.  This  twisting  is  indicative  of  com- 
plexity, and  removes  the  form  possessing  it  from  its  primi- 
tive ancestor.  We  shall  illustrate  the  possible  evolution 
of  the  Gastropod  organism  from  straight  through  loosely 
to  tightly  coiled  and  involute  forms.  Future  research  will 
not  probably  change  the  principle  of  classification,  though 
it  will  doubtless  bring  the  special  forms  selected  into 
genetic  relations,  so  that  each  will  hold  its  proper  place 
in  its  own  particular  series.  We  can  readily  conceive  of 
a  straight  tube  becoming  coiled  so  that  the  whorls  would 
barely  touch  one  another.  In  this  case  the  resultant  form 
would  be  a  smooth  unornamented  spiral.  In  the  loosely 
coiled  shell  of  to-day  (he  margin  of  the  aperture  has  a 
reflected  lip  as  in  Scala  (No.  447,  S.  pretiosa  Linn.). 
This  shell  shows  how  a  tube  may  be  twisted  so  that  the 
whorls  scarcely  come  in  contact.  The  first  whorl  (No. 
447)  is  nearly  smooth,  but  each  successive  whorl  shows  an 
increase  in  the  size  of  the  ridges  till  they  look  like  pro- 
jecting shelves  extending  entirely  around  the  tube.  By 
examining  the  opening,  it  is  seen  that  a  shelf  is  in  reality 
the  lip  of  the  aperture  which  is  made  by  the  mantle  during 
a  period  of  rest. 


SYNOPTIC    COLLECTION. 

Solarium  modestum  Phil.  (No.  448),  exhibits  a  much 
closer  coiling  of  the  tube.  The  youngest  portion  of  the 
shell  which  is  always  at  the  apex  is  smooth  and  polished 
(No.  448).  Each  succeeding  whorl  becomes  consolidated 
with  the  preceding  one  on  the  inner  side,  but  in  turning 
round,  the  tube  leaves  so  large  a  space  in  the  middle 
(called  the  umbilicus)  that  one  can  see  nearly  to  the  apex 
of  the  shell  (No.  449,  S. perspectivum  Lam.). 

Surcula  australis  Roissy  (No.  450),  looks  like  an  inef- 
fectual attempt  to  make  a  perfect  spiral.  The  revolving 
bands  and  lines  are  often  broken  where  additions  have 
been  put  on  at  the  margin.  In  this  way  the  apertures  of 
the  younger  shells  can  be  easily  traced  and  the  length  of 
the  successive  canals  ascertained.  This  irregularity  is 
chiefly  due  to  the  anal  slit  in  the  posterior  end  of  the 
aperture  which  reminds  one  of  the  slit  in  Pleurotomaria, 
Haliotis,  and  the  like.  Most  of  the  members  of  the 
family  Pleurotomidae  to  which  Surcula  belongs,  are  with- 
out a  horny  or  calcareous  operculum  for  closing  the  aper- 
ture, and  this  is  a  characteristic  of  the  deep-sea  forms 
where  the  struggle  for  existence  is  reduced  to  a  minimum 
and  where  therefore  there  is  little  need  of  protection  from 
other  animals.1 

The  shell  of  Lunatia  heros  Adams  (No.  451  ;  see  the 
lowest  shelf  of  the  erect  portion  of  Section  8)  is  a  simple 
spiral  of  a  few  turns,  and  is  open  nearly  to  the  apex. 
The  shell  is  thin  and  covered  by  a  yellowish  brown  layer 
which  is  usually  more  or  less  worn  off.  As  the  shell 
increases  in  size  it  becomes  thicker.  Those  living  on  the 
outer  beaches  where  the  waves  break  with  force  are  much 
larger  and  stronger  than  those  in  quiet  waters.  The 
specimen  (No.  451)  shows  the  large  size  of  the  foot  and 
the  mantle  extending  over  the  edge  of  the  shell.  This 
foot  can  be  completely  withdrawn  into  the  shell  and  the 
aperture  closed  by  a  horny  operculum. 

1  Uall,  Bull.  Mus.  Comp.  Zool.,  XVIII,  1889,  p.  455. 


METAZOA MOLLUSCA.  221 

One  of  the  distinctive  organs  of  the  Gastropods  is  the 
lingual  ribbon  or  odontophore  (No.  452,  odontophore  of 
Lunatia  heros}.  It  is  a  band  armed  on  the  upper  side 
with  chitinous  teeth  and  attached  at  the  back  of  the 
mouth  ;  the  forward  end  is  free.  It  is  used  as  a  rasping 
and  scraping  organ  in  obtaining  food.  One  of  the  many 
classifications  of  the  Gastropods  is  based  on  the  struc- 
ture and  variations  of  the  odontophore. 

Like  Lunatia,  Natica  hebraea  Mart.  (No.  453),  is  a 
simple  spiral  but  the  umbilicus  contains  a  solid  pillar  or 
columella  round  which  the  whorls  of  the  shell  turn.  No. 
454  (Neverita  duplicata  Stimp.,  see  lowest  shelf  of  erect 
part  of  Section)  shows  still  better  than  Lunatia  the  greatly 
distended  muscular  foot.  It  seems  incredible  that  so  large 
an  organ  can  be  contained  in  so  small  a  shell. 

An  instructive  series  is  furnished  by  Polinices  (No.  455, 
P.  mantilla  Linn.)  :  (a)  is  the  young  shell  showing  the 
open  umbilicus ;  a  wire  thrust  into  this  opening^reaches 
upward  nearly  to  the  apex ;  (b)  has  the  umbilicus  still 
visible  though  the  wire  does  not  penetrate  so  near  the 
apex,  showing  that  the  umbilicus  is  becoming  filled  by  the 
columella  which  adheres  to  it  and  is  spirally  twisted ;  at 
this  stage  the  inner  lip  has  a  sharp  edge.  In  (c)  the 
umbilicus  is  entirely  concealed  by  the  thickened  inner 
lip ;  in  this  specimen  the  horny  operculum  is  in  place  ; 
the  lines  of  growth  near  the  margin  are  fine  and  close 
together  while  in  (d)  which  likewise  has  the  umbilicus 
concealed,  the  lines  of  growth  are  coarser.  No.  455  e, 
is  probably  a  reduced  form ;  although  about  a  third 
smaller  than  (d),  its  weight  is  essentially  the  same,  and  a 
thick  heavy  deposit  is  laid  on  over  the  umbilicus.  This 
series  shows  that  the  open  umbilicus  is  a  primary  con- 
dition and  the  concealed  umbilicus  is  secondary.  This 
furnishes  a  good  phylogenetic  reason  for  placing  those 
shells  with  the  open  umbilicus  as  more  generalized  in  a 
system  of  classification. 

The  next  group  of  plain  but  tightly  coiled  shells  with- 


222  SYNOPTIC    COLLECTION. 

out  umbilicus  is  represented  in  the  Collection  by  a  number 
of  specimens  which  may  belong,  as  we  have  already 
pointed  out,  to  as  many  different  series. 

lanthina  has  a  spiral  shell  resembling  Lunatia  in  shape. 
It  is  translucent  with  violet  colored  areas.  This  mollusc 
makes  a  swimming  float  of  cartilaginous  air  sacs  which 
serves  to  keep  it  at  the  surface.  To  the  under  surface 
of  this  float  are  attached  the  egg  capsules  (see  No.  456). 

The  egg  cases  (No.  457  ;  see  erect  part  of  Section)  of 
Buccinum  undatum  Linn.,  are  in  masses.  The  shell  is 
closely  coiled  and  ribbed  at  right  angles  to  the  lines  of 
growth  (see  No.  458). 

Turbo  setosus  Gmel.  (No.  459)  begins  as  a  smooth,  col- 
orless or  yellow  shell,  then  becomes  ridged  and  is  of  a 
vivid  green  color,  while  the  older  whorls  are  dark  green, 
marked  by  reddish  brown  spots.  The  aperture  is  entire. 
Litorina  littorea  Linn.,  has  been  imported  from  Europe, 
and  in  1872  appeared  in  Massachusetts;  since  then  it  has 
spread  with  remarkable  rapidity.  The  British  form  (No. 
460,  L.  obtusata  Linn.),  is  a  smooth  spiral  without  an  um- 
bilicus. The  shape  varies  like  that  of  most  littoral  species, 
some  specimens  having  a  spire  of  three  or  four  whorls, 
while  in  others  the  spire  is  depressed  so  that  all  the  whorls 
excepting  the  last  or  body  whorl  are  on  a  horizontal  plane. 
Our  New  England  species  generally  has  a  sharp  spire  and 
revolving  lines  on  the  whorls,  while  the  color  is  a  dingy 
brown  or  red.  The  external  horny  layer  when  fresh  is  a 
chestnut  brown. 

Cydostoma  elegans  Drap.  (No.  461  model),  is  similar  to 
Litorina  in  many  structural  points  but  it  has  become  more 
specialized  by  losing  gills  and  breathing  air  by  means  of 
lungs.  In  a  classification  based  strictly  upon  the  struc- 
ture of  the  breathing  organs  the  Cyclostoma  would  be 
placed  with  the  Pulmonifera,  but  it  is  not  probable  that 
this  would  indicate  its  relationships.  The  model  repre- 
sents the  animal  with  the  foot  expanded  ;  at  the  anterior 
end  is  the  head  with  two  tentacles  extended,  at  the  base 
of  which  are  the  eyes. 


METAZOA MOLLUSCA.  223 

Fulgur  (Nos.  462-465,  F.  canaliculatum  Say),  places  its 
eggs  in  horny  sacs  or  capsules  which  it  fastens  together  in  a 
long  string  (No.  463;  see  lowest  shelf).  These  maybe 
opened  and  the  young  (No.  462)  observed  in  different 
stages  of  development.  The  specimens  possess  a  smooth 
rounded  protoconch,  so  thin  and  translucent  as  to  show 
the  yellow  body  within.  The  succeeding  whorl  is  ribbed, 
and  extends  into  a  long  canal  giving  the  shell  a  pear-like 
shape  which  remains  essentially  the  same  in  older  stages 
(Nos.  464,  465).  The  model  (No.  465,  placed  on  account 
of  size  at  the  back  of  the  Section  on  the  right)  shows  the 
large  foot  extended  as  in  the  act  of  crawling ;  the  head 
with  its  tentacles ;  the  mantle  on  the  edge  of  the  shell ;  and 
the  siphon  in  the  long  canal. 

Fasciolaria  is  nearly  related  to  Fulgur  and  its  exquisite 
egg  cases  are  seen  in  No.  466  (see  erect  portion  of  Sec- 
tion) .  This  species  (F.  tulipa  Linn.)  fastens  these  flower- 
like  cases  to  some  foreign  object,  —  coral  in  this  instance. 
Across  the  free  end  of  the  tube,  stretches  a  membrane 
which  opens  when  the  young  are  ready  to  escape. 

Magilus  antiquus  Mont,  is  a  reduced  form,  the  reduc- 
tion being  due  most  probably  to  the  habit  of  living 
in  coral.  The  young  shell  (PL  467)  is  a  thin  spiral  of 
three  or  four  whorls,  proving  that  its  more  immediate 
ancestors  had  a  spiral  shell.  The  latter  is  similar  to 
that  of  Natica,  Buccinum,  and  the  like,  and  for  this  reason 
it  is  placed  near  them.  In  order  to  keep  on  a  level  with 
the  surface  of  the  growing  coral,  Magilus  ceases  to  revolve, 
and  puts  out  a  long,  nearly  straight  tube  (No.  468).  As 
it  advances  with  the  new  growth  it  fills  up  the  spiral  and 
tube  behind  it. 

The  veliger  stage  of  Astyris  (Pis.  469,  470,  x  100 
diameters ;  the  colors  are  schematic),  shows  the  large 
lobed,  ciliated  velum,  so  characteristic  of  this  stage  of 
Gastropods,  and  the  spiral  shell.  The  adult  (No.  471) 
has  a  shell  with  few  whorls.  The  model  represents  the 
animal  as  walking  on  the  sand  with  extended  foot,  ten- 
tacles, and  siphon. 


224  SYNOPTIC    COLLECTION. 

In  Terebra  and  Turritella  we  have  illustrations  of  a 
perfect  spiral  of  many  whorls  without  projecting  orna- 
mentation in  the  form  of  spikes  or  flutings.  In  Terebra 
subulata  Lam.  (No.  472),  the  early  whorls  are  nearly 
colorless  but  those  succeeding  are  marked  by  deep  red 
spots.  Both  the  young  and  adult  shells  are  smooth,  not 
having  even  the  revolving  lines  and  ridges  seen  in  Turri- 
tella (No.  473  ;  in  this  shell  the  youngest  specimen  has 
nineteen  whorls  and  the  one  with  the  largest  body  whorl 
only  sixteen,  showing  that  the  youngest  whorls  are  broken 
off).  The  margin  is  entire  in  both  genera.  Cerithium 
tuberosum  Fabr.  (No.  474),  has  the  revolving  lines  of 
Turritella  and  in  addition  the  vertical  ridges.  The  mar- 
gin has  a  short,  slightly  recurved  canal. 

Vermicularia  begins  its  life  with  a  tightly  coiled  shell 
(see  No.  475,  V.  spirata  Phil.)  that  is  similar  to  Turritella. 
Living  in  the  cavities  of  a  sponge  it  needs  to  keep  at  the 
surface  of  the  growing  animal  in  order  to  obtain  food. 
It  succeeds  in  doing  this  by  forming  a  loosely  coiled  shell 
(No.  475)  or  in  growing  straight.  We  have  here  and  in 
Magilus  similar  conditions  producing  similar  results,  and 
both  are  good  illustrations  of  adaptation  of  structure  to 
habit. 

On  the  west  coast  of  Florida,  Vermetus  lumbricalis,  var. 
nigricans  Dall,  forms  rock-like  masses,  as  shown  in  No. 
476  (which,  on  account  of  its  size,  is  placed  at  the  back 
of  Section  8) .  When  in  the  water  the  tubes  are  erect. 
The  greater  part  of  each  tube  is  straight  though  some  of 
the  tubes  show  a  spiral  structure  at  the  smaller  end. 

Gyrineum  spinosum  Lam.  (No.  477),  has  a  colorless, 
smooth,  snail-like  spiral  at  the  apex,  the  general  appear- 
ance of  which  is  distinctively  unlike  the  succeeding  whorls. 
The  latter  are  somewhat  flattened  and  have  vertical  ridges 
or  varices  with  intervening  short  knobs  and  spikes.  Ac- 
cording to  Adams  the  shells  that  are  armed  with  these 
knobs  are  found  in  rocky  places,  while  the  smoother  spec- 
imens come  from  deep  waters. 


METAZOA MOLLUSCA. 

Murex  (No.  478,  M.  tenuispina  Lam.),  is  an  illustration 
of  a  specialized  shell  of  this  group.  In  this  species  the 
protoconch  is  preserved  as  a  tiny  white  pearly  shell. 
Extending  below  this  are  two  or  three  whorls  with  ridges 
but  without  the  long  slender  projections  which  ornament 
the  succeeding  whorls  to  an  extreme  degree. 

Conus  bandanus  Brug.  (No.  479),  is  like  an  inverted 
cone,  the  last  whorl  being  large  and  making  most  of  the 
cone.  The  number  of  whorls  can  be  indistinctly  traced, 
encircling  the  apex  at  the  broad  posterior  end.  The  aper- 
ture is  neither  notched  nor  drawn  into  a  long  canal. 

Trochus  (=.  Tectus)  fenestratus  Gmel.  (No.  480),  is  a 
tightly  coiled  tube,  the  whorls  increasing  in  number  and 
being  uniform  in  ornamentation. 

Aulica  deshayesi  Reeve  (No.  481),  is  a:n  instructive 
species  since  the  protoconch  is  so  large  that  its  distinctive 
characters  can  be  seen  and  thereby  the  ancestral  form  of 
the  genus  determined.  This  embryonic  shell  is  a  plump, 
globular  spiral,  light  colored  and  smooth,  and  revolves  in 
a  different  plane  from  the  rest  of  the  shell.  One  can  dis- 
tinctly make  out  where  the  nepionic  stage  begins  by  not- 
ing the  origin  of  the  revolving  lines  and  vertical  ridges. 
The  ephebic  stage  lasts  until '  the  ridges  begin  to  dis- 
appear, as  seen  in  No.  481.  The  vertical  markings 
become  coarser,  which  are  characters  of  the  gerontic 
stage.  Oliva  erythrostoma  Lam.  (No.  482),  is  similar  in 
the  different  stages,  as  shown  in  the  specimens,  but  by 
examining  the  apex,  a  colorless  translucent  spiral  is  seen 
which  represents  the  ancestral  form.  The  last  whorl  con- 
stitutes most  of  the  visible  shell,  but  the  number  of  whorls 
encircling  the  apex  can  be  easily  counted.  The  specimens 
show  considerable  variation  in  color. 

The  resemblance  of  Oliva,  Aulica,  and  the  like  to  the 
young  Cypraea  argues  for  a  close  relationship  between 
these  forms. 

In  Cymbium  cymbium  Linn.  (No.  483),  the  apex  is 
smooth  and  flattened,  and  only  two  whorls  are  visible. 


226  SYNOPTIC    COLLECTION. 

The  shell  is  notched  and  the  animal  has  a  short  siphon. 
According  to  Adanson l  many  living  Cymbia  were  found 
with  living  young  in  their  bodies,  thus  proving  them  to 
be  viviparous.  The  young  (there  are  only  four  or  five  in 
each  Cymbium)  leave  the  mother  when  the  shell  is  an 
inch  long. 

Strombus  costatus  Gmel.  is  a  plain  spiral  in  which  the 
whorls  can  be  readily  counted.  The  aperture  of  the 
adult  extends  upward  on  the  preceding  whorl  and  be- 
comes flaring  with  a  recurved  canal.  No.  484  is  an 
antero-posterior  section  through  the  middle  of  the  shell, 
showing  the  internal  structure,  and  No.  485  is  a  cross 
section  of  another  species,  S.  gigas. 

Pteroceras  lambis  Linn,  carries  this  mode  of  develop- 
ment farther  than  Strombus.  It  is  illustrated  by  a  fine 
series  (No.  486)  showing  marked  changes  between  the 
young  and  adult  stages:  (a)  is  a  plain  spiral  having  a 
long,  narrow,  notched  aperture  with  a  thin,  sharp,  unorna- 
mented  margin ;  (b)  is  the  dorsal  side,  showing  yellowish 
color  banded  with  red ;  (c-f)  all  exhibit  the  plainness  of 
slightly  older  shells.  In  (g)  the  margin  of  the  aperture 
extends  toward  the  apex  as  in  Strombus,  and  in  (h)  and 
(i)  it  goes  beyond  it,  changing  essentially  the  shape  of 
the  shell  and  giving  a  wide,  flaring  aperture  with  a  canal 
at  either  end.  The  margin  becomes  fluted  at  first  and 
afterward  extends  outward  in  long,  half  open  canals 
which  finally  become  closed  solid  spines2  (see  j  and  k). 

Phalium  inflata  Shaw  (No.  487),  has  the  first  whorls 
light  colored  and  plain ;  those  succeeding  may  have  the 
marks  of  the  lip  or  not,  one  being  without  them  and  two 
having  them.  The  canal  is  short  and  instead  of  being 
prolonged  as  in  Murex,  it  is  sharply  recurved. 

No.  488  is  a  section  of  a  small  specimen  of  Cassis 
cameo  Stimp.  Cassis  grows  to  a  large  size  and  is  much 
used  in  making  cameos. 

1  See  Adams,  Genera  of  Moll.,  I,  1858,  p.  158. 

2  Adams,  loc.  cit.,  I,  p.  260. 


METAZOA  —  MOLLUSCA.  227 

The  series  of  Cypraea  cervus  Linn.  (No.  489  a-c)  is 
extremely  instructive.  The  young  shell  (a)  is  a  spiral 
in  which  the  number  of  whorls  can  be  easily  counted. 
A  still  earlier  stage,  of  which  there  is  no  specimen,  is  a 
simple,  thin,  snail-like  spiral  (Adams).  The  shape  of  (a) 
is  similar  to  Oliva,  Cymbium,  and  the  like.  The  aperture 
is  also  long  with  a  thin,  sharp,  untoothed,  and  unorna- 
mented  margin,  and  a  slight  notch  at  the  anterior  end. 
In  (b)  the  shape  has  changed,  the  margin  of  the  aperture 
has  thickened  and  turned  inward,  while  both  sides  of  the 
opening  are  toothed  and  both  ends  notched.  In  (c)  only 
vestiges  of  the  spiral  remain,  which  no  one  would  recog- 
nize who  had  not  seen  the  younger  stages;  thus  the  shell 
has  taken  on  a  character  that  separates  it  from  those  pre- 
viously described  and  which  places  it  with  the  more  spe- 
cialized forms.  If  a  vertical  section  of  the  shell  is  made, 
the  whorls  are  seen  inside  (No.  490,  C.  exanthema  Linn.) 
concealed  by  the  last  body  whorl.  No.  489  c  is  of  re- 
markable size  and  is  lighter  in  weight  than  some  of 
smaller  size. 

It  is  thus  seen  that  the  development  of  Cypraea  is  an 
epitome  of  the  life  history  of  those  Gastropods  which 
have  a  simple,  snail-like  spiral  in  adult  life,  and  of  those 
with  the  modified  spiral  of  Oliva  and  Cymbium. 

A  still  more  specialized  form  is  Cypraea  mauritiana 
Linn.  Its  development  is  shown  in  the  series  No.  491. 
The  first  six  specimens  would  hardly  be  called  the  young 
of  the  last  six,  so  unlike  are  they  in  shape  and  coloring. 
In  the  youngest  specimen  in  the  series,  the  spire  with  its 
small  whorls  and  large  body  whorl  is  seen.  The  shell 
is  now  strikingly  like  Oliva.  The  long  aperture  has  a 
sharp  margin  which  as  yet  has  not  turned  inward.  In 
the  older  stages  the  shape  changes ;  the  early  spiral  is 
concealed  by  the  enamel  which  the  mantle  has  laid  on. 
There  are  two  broad,  thick,  flat,  toothed  lips  with  a  nar- 
row aperture  and  a  canal  at  either  end.  The  two  largest 
specimens  have  grown  high  vertically,  and  this  peculiar 


2*28  SYNOPTIC    COLLECTION. 

shape  with  the  flattened  lips  makes  the  shell  more  spe- 
cialized than  those  of  the  other  species  of  Cypraea  already 
described.  Cypraea  is  a  transitional  form  between  those 
shells  that  have  the  external  spiral  represented  by  the 
young  and  those  which  have  the  spiral  partly  or  wholly 
internal,  being  covered  by  the  growth  of  the  later  whorls. 

Ultimus  gibbosa  Linn.  (No.  492),  does  not  show  even 
in  youth  any  embryonic  shell  or  spiral.  The  shell  re- 
volves so  that  each  whorl  covers  the  preceding.  The 
margin  of  the  aperture  is  thin  and  easily  broken.  In 
course  of  growth  the  margin  thickens  and  turns  inward, 
so  that  the  adult  has  a  strong  incurving  lip. 

A  related  species,  Simnia  acicularis  Lam.  (No.  493), 
offers  a  striking  example  of  mimicry.  In  the  present 
instance  it  has  taken  on  the  uniform  deep  purple  color  of 
the  coral  on  which  it  lives.  When  it  chooses  the  yellow 
coral,  Rhipidogorgia,  for  its  home,  it  assumes  the  yellow 
color,  and  on  white  coral  it  is  nearly  white.  Its  foot  is 
narrow  and  well  adapted  for  clinging  to  the  coral. 

Transitional  forms  between  marine  Gastropods  and 
fresh-water  or  land  species  are  found  in  Nerita,  Neritina, 
and  the  like.  The  transition  from  the  one  to  the  other 
is  governed  by  natural  causes  which  we  have  already 
found  are  not  difficult  to  explain. 

The  youngest  portion  of  the  shell  of  Nerita  versicolor 
Gmel.  is  yellow,  smooth,  and  unmarked  by  color  spots, 
as  seen  in  the  first  whorl  of  No.  494.  In  the  next  whorl 
the  surface  is  ridged,  and  the  color  is  nearly  white  marked 
by  dark  irregular  spots.  The  teeth  on  the  left  of  the 
aperture  are  barely  indicated  and  none  are  seen  on  the 
right  side.  In  (b)  the  ridges  are  more  pronounced  and 
there  are  suggestions  of  teeth  on  the  right  side.  In  (c) 
the  youngest  portion  is  colorless,  as  is  the  case  with  a 
number  of  the  older  forms  ;  (e)  has  a  predominance  of 
red  color  over  the  .darker  shade  of  the  youngest  shell, 
and  the  teeth  on  both  sides  are  well  developed;  (g)  and 
(h)  illustrate  the  variation  in  color  from  a  light  to  a  dark 


METAZOA MOLLUSCA.  229 

shell.  This  subject  of  color  variation  in  a  single  species 
is  shown  still  better  by  Nerita peloronta  Linn.  (No.  495). 
Here  we  have  nineteen  shells  varying  from  a  nearly  white 
shell  spotted  here  and  there  with  pink  to  a  dark  purplish 
shell  apparently  banded  and  spotted  with  lighter  shades. 
The  youngest  stage  in  all  the  specimens  is  either  white 
or  yellow,  without  spots  or  bands,  and  is  smooth  ;  (y) 
and  (z)  are  in  their  natural  state,  while  the  others  have 
been  boiled  in  caustic  potash  for  about  ten  minutes,  so 
that  these  bright  colors  are  not  seen  in  the  living  ani- 
mals ;  (z)  is  an  adult  which  is  mounted  to  show  the  bright 
red  spot  near  the  large  tooth  that  has  given  the 'name  of 
Bleeding  Tooth  to  this  species,  and  also  the  operculum 
which  is  in  place  and  is  deeply  colored,  (q)  is  an  illus- 
tration of  albinism',  the  spot  that  is  usually  blood  red 
being  nearly  colorless. 

Neritina  (No.  496,  N.  canalis  Sowb.),  is  a  genus  of 
especial  interest  since  some  of  the  species  live  in  the 
saltest  of  sea  water,  that  of  a  lagoon,  while  most  are 
either  brackish  or  fresh-water  or  land  animals.  Certain 
marine  species  are  practically  land  animals,  since  they 
live  where  they  cannot  be  immersed  in  water  excepting 
at  extremely  high  tides,  and  even  then  they  would  not  be 
covered  unless  the  waves  dash  upon  the  rocks  where  they 
live.  Adams1  speaks  of  some  species  living  in  trees  over- 
hanging water. 

The  shell  of  Neritina  canalis  Sowb.  (No.  496),  is  cov- 
ered by  a  thick,  dark  brown  horny  layer  which,  when 
broken  off,  reveals  a  shell  of  peculiar  whiteness. 

Pulmonifera.  Many  Gastropods  that  were  originally 
marine  animals  have  doubtless  become  in  the  course  of 
many  generations,  and  a  longer  or  shorter  period  of 
time,  fresh-water  or  land  animals.  Most  of  these  now 
bear  the  name  of  Pulmonifera,  since  they  no  longer 
breathe  air  dissolved  in  water,  but  are  equipped  with 

1  Genera  of  Moll,  I,  1858,  p.  381. 


230  SYNOPTIC    COLLECTION. 

primitive  lungs  in  the  form  of  a  pulmonary  sac  or  cavity. 
As  a  proof  that  the  Pulmonifera  are  more  specialized 
than  the  groups  already  described,  it  may  be  stated  that 
many  Pulmonates  fill  their  lung  sac  with  fresh  water  in 
the  younger  stages  and  only  later  in  life  dispense  with 
the  water.  There  are  objections  to  the  use  of  the  term 
Pulmonifera,  since  some  of  the  air-breathing  Gastropods 
(Cyclostoma,  for  instance;  -see  No.  461)  are  so  different 
in  structure  from  the  typical  Pulmonifera  that  they  can- 
not be  placed  in  this  group  but  are  specialized  air-breath- 
ing members  of  more  generalized  groups. 

As  a  rule  the  shells  of  the  Pulmonifera  do  not  attain 
that  brilliancy  of  coloring  and  that  extreme  ornamenta- 
tion which  may  be  observed  in  their  marine  ancestors. 

Among  the  fresh-water  and  land  Gastropods  there  are 
no  forms  possessing  the  straight  cone-like  shell,  but  the 
shallow  cup  of  Patella  and  the  spiral  of  Crepidula  are 
represented  by  Ancylus  and  Gundlachia.  These  Gastro- 
pods have  habits  similar  to  those  of  their  marine  relatives 
and  the  structure  is  similar.  We  have  not  found  a  spiral 
so  loosely  coiled  as  Scala ;  the  majority  represent  the 
group  of  tightly  coiled  plain  spirals,  the  chief  difference 
between  the  genera  being  in  the  plane  of  the  coiling. 

Ampularia  globosa  Swains.  (No.  497),  is  a  simple  spiral 
with  a  small  umbilicus,  holding  a  similar  place  among 
fresh-water  univalves  that  Lunatia  holds  among  the  ma- 
rine. The  glossy,  horny  layer  of  this  genus  is  striking, 
reminding  one  of  this  finely  developed  layer  on  fresh- 
water bivalves.  The  operculum  of  the  young  and  the 
adult  shell  is  not  spiral,  but  the  additions  are  made  con- 
centrically (see  No.  497). 

In  this  genus  the  left  gill  is  vestigial,  the  mantle  cavity 
having  a  large  pulmonary  sac  on  each  side.  These  mol- 
luscs are  amphibious,  being  able  to  live  a  long  time  out 
of  water. 

Another  fresh-water  form  is  the  pond  snail,  Limnaeus 
stagnalis  O.  F.  Mull.  (No.  498) .  It  comes  to  the  sur- 


METAZOA MOLLUSCA.  231 

face  for  air,  but  whether  this  is  a  necessity  for  maintain- 
ing life  is  not  yet  settled.  The  model  shows  the  long 
respiratory  tube  containing  bubbles  of  air  which  the  snail 
extends  from  the  respiratory  opening  to  the  surface  of  the 
water.  The  tentacles  are  flattened,  as  seen  in  No.  498. 
When  ponds  dry  up,  these  snails  bury  themselves  in  the 
mud  and  in  this  situation  can  live  for  a  considerable  time. 

Planorbis  corneus  Linn.  (No.  499),  is  a  good  example 
of  a  shell  coiled  on  a  horizontal  plane.  The  whorls  are 
few  in  number  and  the  aperture  is  entire  and  flaring. 
Polygyratia  polygyrata  Bonn.  (No.  500),  is  a  still  better 
example  of  a  horizontal  spiral  consisting  of  eight  closely 
coiled  whorls  with  the  ninth  unfinished.  The  aperture 
like  that  of  Planorbis  is  entire. 

Campeloma  (No.  501,  C.  decisa  Say)  and  Melania  (No. 
502,  M.  hastata  Lea),  are  exceptional  Gastropods,  inas- 
much as  both  are  viviparous.  Vivipara  (=  Paludina) 
carries  its  young  about  with  it  for  three  or  four  weeks 
after  birth. 

The  land  Gastropods  are  represented  by  a  number  of 
species.  Helicostyla  leai  Pfr.  (No.  503),  is  a  smooth 
beautiful  white  spiral  of  three  or  four  whorls.  The  aper- 
ture is  entire,  and  there  is  no  umbilicus.  The  eggs  of 
this  genus  are  protected  by  a  limy  shell  so  that  they  re- 
semble those  of  birds. 

Helix  (No.  504)  is  one  of  the  commonest  land  snails. 
The  youngest  shells  (see  No.  504)  are  so  thin  and  fragile 
that  they  can  be  easily  crushed  between  the  fingers.  The 
margin  is  sharp  and  lipless.  When  older  the  shell  is 
stouter  with  a  thick  white  lip  (No.  504).  The  last  speci- 
men in  the  upper  right  hand  corner  is  reduced,  being 
small  in  size  but  provided  with  the  thickened  lip.  The 
adult  animal  (No.  505,  H.  hortensis  O.  F.  Mull. ;  No.  506, 
H.  pomatia  Linn.,  see  topmost  shelf),  is  represented  with 
foot  extended,  and  with  the  shell  containing  the  spiral 
portion  of  the  body  in  normal  position  when  the  snail  is 
crawling.  The  head  has  two  pairs  of  tentacles,  and  the 


232  SYNOPTIC    COLLECTION. 

black  eyes  are  distinctly  seen  at  the  ends  of  the  longer 
pair.  No.  507  is  a  model  showing  the  internal  organs  of 
Helix  pomatia  Linn.  The  various  parts  are  marked  ; 
those  on  the  left  are  the  buccal  body,  esophagus,  salivary 
glands,  stomach,  liver,  intestine,  and  the  pulmonary  cham- 
ber ;  and  those  on  the  right  the  reproductive  organs  and 
slime  glands. 

The  land  Gastropods  most  specialized  by  reduction  are 
the  slugs,  represented  by  Limax  (Nos.  508-511).  Here 
the  shell  is  reduced  to  a  thin,  flat  plate  on  the  back  (see 
model  of  Limax  maximus  Linn.,  No.  508),  and  this  has 
become  internal.  The  spiral  body  of  most  Gastropods 
no  longer  exists,  but  the  body  of  the  slug  is  long  with  the 
foot  on  the  ventral  side  (No.  509,  L.  flavis  Linn.).  The 
preparation  (No.  510)  shows  the  general  anatomy  of 
Limax  rufus,  while  the  genital  organs  are  seen  in  No. 

5"- 

Section  9  of  Case  B  is  taken  up  with  the  Tectibranchs, 

Nudibranchs,  Scaphopoda,  Heteropoda,  and  Pteropoda. 
These  are  considered  as  so  many  groups  of  molluscs  which 
have  become  modified,  each  in  its  own  special  and  dis- 
tinctive way,  to  meet  the  requirements  of  existence.  The 
Pteropods  are  probably  the  most  specialized,  and  the  most 
closely  related  to  the  Cephalopods;  but  on  account  of 
their  minute  size,  they  are  placed  in  the  horizontal  part 
of  Section  9.  Here  they  can  be  seen  and  studied  more 
easily  than  in  the  erect  portion,  where,  according  to  our 
system,  they  properly  belong. 

Some  of  the  Tectibranchs  have  well  developed  shells, 
like  Tornatella  (No.  512,  T.  solidula  Lam.)  and  Bullus 
(No.  513,  B.  oblongus  A.  Adams),  while  in  others 
(Aplysia,  No.  514,  see  erect  part  of  Section,  No.  515,  and 
Pleurobranchus,  No.  516)  the  shell  exists  only  as  a  vestige. 
Tornatella  (No.  512),  reminds  one  of  Oliva  (No.  482)  with 
its  short  spire  and  large  body  whorl.  Bullus  (No.  513) 
even  when  young  shows  no  spiral  form,  but  if  a  cross 
section  of  the  shell  is  made  near  the  posterior  end  the 


METAZOA MOLLUSCA.  233 

spiral  is  seen  within.  Every  whorl  entirely  conceals  the 
preceding,  as  we  have  seen  it  in  Ultimus  (No.  492). 

The  "sea-hare,"  Aplysia  (No.  514,  A.  limacina;  No. 
515,  A.  inca  d'Orb.)  has  only  the  remnant  of  a  shell  on  its 
back  in  the  form  of  a  concave  plate,  and  this  is  concealed 
by  a  fold  of  the  mantle.  On  the  dorsal  side  the  mantle 
grows  out  into  two  large  folds,  called  epipodia  (see  Nos. 
514,  515)  which  are  used  in  swimming.  The  single 
branchia  is  on  the  back  protected  by  the  mantle.  The 
model  (No.  515)  represents  the  animal  as  crawling  on  its 
long  ventral  foot.  Garstang 1  has  pointed  out  the  interest- 
ing fact  that  young  Aplysiae  in  migrating  during  growth 
from  deep  water  to  the  shore  pass  through  algae  colored 
first  red,  then  brown,  and  finally  olive  green,  and  that 
these  animals  change  their  colors  from  red  to  green  in 
accordance  with  their  surroundings. 

The  shell  is  reduced  and  concealed  by  the  mantle  in 
Pleurobranchus  (No.  516,  P.  grandis  Pease).  Lobiger 
(No.  517,  L.  picta  Pease),  has  a  small  shell  on  its  back  and 
two  pairs  of  wing-like  swimming  organs  extending  from 
the  sides  of  the  body. 

NUDIBRANCHS. 

The  Nudibranchs  pass  through  a  trochophore  and  veli- 
ger  stage  in  their  development.  They  possess  a  spiral  or 
nautiloid  shell  before  they  leave  the  egg,  and  the  body  at 
this  time  is  more  or  less  spiral  in  form.  During  the  growth 
of  the  larva  the  shell  disappears  and  the  animal  extends 
lengthwise.  The  possession  of  a  shell  in  the  embryo  is 
evidence  that  the  Nudibranchs  have  descended  from 
Gastropods  with  spirally  coiled  shells.  According  to 
Kingsley2  the  twisting  or  torsion  of  the  body  has  not  been 
carried  to  its  full  extent,  which  would  indicate  a  primitive 

1  Journ.  Mar.  Biol.  Assoc.,  n.  s.,  I,  1889-90,  p.  411. 

2  Stand.  Nat.  Hist.,  I,  1885,  p.  295. 


234  SYNOPTIC    COLLECTION. 

condition.  But  inasmuch  as  this  torsion  is  greater  in  the 
embryo  than  in  the  adult,  the  less  degree  of  twisting  is  a 
reduced  rather  than  a  primitive  characteristic.  The  asym- 
metrical condition  of  the  heart  and  the  nephridium  prove 
that  the  bilateral  symmetry  of  the  adult  is  also  a  second- 
arily acquired  and  not  a  primitive  condition.  Gilchrist1 
has  shown  that,  while  the  original  bilateral  symmetry  is 
apparently  assumed,  the  organs  which  were  lost  on  one 
side  in  the  twisting  of  the  straight  body  into  a  spiral  are 
never  again  developed. 

Not  only  has  the  Nudibranch  lost  its  shell,  but  in  some 
species  the  mantle  has  disappeared. 

In  other  ways  this  group  has  become  peculiarly  special- 
ized. Many  Nudibranchs  are  without  true  tentacles,  while 
most  have  organs  called  dorsal  tentacles  or  rhinophores 
which  are  supposed  to  be  organs  of  smell.  The  branchiae 
are  not  like  the  gills  of  most  molluscs,  but  are  secondarily 
acquired,  respiratory  organs,  and  are  often  called  cerata 
to  distinguish  them  from  the  primitive  gill.  These  bran- 
chiae vary  greatly  both  in  shape  and  position  and  are 
often  extremely  beautiful  organs. 

Eolis  (  =  Aeolis)  coronata  Forbes  lays  its  eggs  in  a 
close-set  spiral  coil  of  four  volutions  (PI.  518,  fig.  i  ;  fig. 
2,  a  portion  of  the  same  magnified,  showing  the  eggs 
imbedded  in  a  gelatinous  thread).  The  larva  (fig.  3)  is 
provided  with  a  spiral  shell  (fig.  4),  which  is  closed  by 
an  operculum.  At  this  stage  the  larva  has  the  two  ciliated 
oral  lobes  which  aid  in  locomotion.  With  the  growth 
of  the  animal  the  shell  and  operculum  disappear  and  the 
oral  lobes  are  either  modified  or  wholly  absorbed.  The 
mature  Eolis  (fig.  5,  upper  side;  fig.  6,  lower  side;  No. 
519,  E.  papillosa  Loven),  has  a  long  slug-like  body  wholly 
unprotected  by  a  calcareous  or  horny  shell.  The  forward 
part  bears  a  pair  of  tentacles,  and  also  a  pair  of  rhinophores 
or  dorsal  tentacles.  Along  the  back  the  brilliantly  col- 

1  Proc.  Roy.  Soc.  Edinburgh,  XX,  1895,  p.  368. 


METAZOA MOLLUSCA.  "235 

ored  branchiae  are  arranged  in  six  clusters,  each  cluster 
consisting  of  many  papillae.  These  branchiae  are  liable 
to  fall  off,  and  sometimes  a  whole  cluster  is  wanting,  In 
Flabellina  (No.  520,  F.  janthina  Angas),  a  related  form, 
the  branchiae  are  ^numerous  and  tube-like,  as  they  are 
also  in  Spnrilla  neapolitana  (No.  521). 

The  branchiae  in  Gtaucus  longicornis  Reinh.  (No.  522), 
are  in  the  form  of  clusters  of  long  slender  filaments  on 
either  side  of  the  tapering  body.  These  branchiae  are 
not  only  respiratory  organs  but  are  used  for  swimming 
when  the  little  creature  with  ventral  side  uppermost  darts 
through  the  water. 

Tethys  leporina  Linn.  (No.  523),  is  a  Nudibranch  of 
rare  beauty.  It  is  nearly  transparent,  with  light  and  dark 
red  spots.  The  forward  part  is  broad  and  has  a  delicate 
fringe.  The  dorsal  tentacles  are  leaf-like  and  the  bran- 
chiae extend  down  the  body  on  either  side.  At  the  pos- 
terior end  the  mantle  is  extended  into  an  excurrent  siphon. 
Melibe  (No.  524,  M.  fimbriata  Aid.  &  Hanc.)  has  the 
head  differentiated  from  the  body  ;  it  bears  two  prominent 
dorsal  tentacles  enlarged  at  the  end.  The  body  is  cov- 
ered with  papillae,  and  along  each  side  are  large  club- 
shaped  branchiae,  which  after  the  first  pair  are  placed 
alternately.  . 

Dendronotus  arborescens  Mull.  (No.  525),  is  similar  in 
many  respects  to  Eolis.  When  young  it  is  nearly  color- 
less, but  the  adult  is  subject  to  much  variation  in  color ; 
usually,  however,  it  is  reddish,  as  seen  in  No.  525. 

The  head  is  provided  in  front  with  branched  append- 
ages. Above  are  the  dorsal  tentacles  which  can  be 
withdrawn  into  sheaths.  Along  each  side  of  the  body  are 
the  arborescent  branchiae.-  The  long  tapering  foot  is 
well  adapted  for  clasping  seaweed  and  is  used  in  this 
way  as  well  as  in  crawling. 

Scyllaea  marmnrata  Aid.  &  Hanc.  (No.  526),  is  a 
small  Nudibranch  with  two  pairs  of  gills.  The  animal 
resembles  the  Sargassum  sea-weed  in  which  it  lives,  and 


236 


SYNOPTIC    COLLECTION. 


its  long  narrow  foot  with  thin  and    flexible  sides  is  well 
adapted  for  clasping  the  stems  of  algae. 

The  branchiae  in  Pleurophyllidia  (No.  527,  P.  setnperi 
Bergh),  consist  of  leaf-like  organs  on  each  side  of  the 
body  between  the  foot  and  the  doreal  portion  of  the 
mantle.  In  Doris  (No.  528,  D.  nubilosa  Pease)  they 
form  a  circle  around  the  anus  and  are  retractile,  while  in 
Trevelyana  (No.  529,  T.  cristata  Bergh)  and  Plocamo- 
phorus  (No.  530,  P.  imperialis  Angas)  they  are  not  so 
completely  retractile,  although  according  to  Eliot,1  they 
retract  when  touched  in  the  living  animal,  but  remain  out- 
side in  alcoholic  specimens. 

Among  the  Nudibranchs  that  have  lost  both  shell  and 
branchiae  are  Phyllobranchus  (No.  531,  P.  orientalis 
Kol.)  and  Elysia  (No.  532,  E.  chlorotica  Gould)  ;  while 
in  Pontolimax  (  =  Limapontia)  (No.  533,  P.  capitatus  O. 
F.  Mull.)  no  shell,  branchiae,  nor  appendages  exist. 

It  is  interesting  to  note  that  the  law  of  acceleration  in 
development  has  brought  about  a  condensation  of  embry- 
onic stages  in  two  Nudibranchs,  Cenia  cocksi  and  PeJta 
coronata?  so  that  the  veliger  stage  with  the  ciliated  velum 
and  the  shell  is  omitted  from  the  ontogeny. 


SCAPHOPODA. 

The  Scaphopoda  are  a  small  group  represented  by  Den- 
talium  (Nos.  534-536).  The  tube  like  shell  of  this  genus 
is  not  made  by  the  addition  of  successive  layers  to  the 
margin  of  a  cone-like  embryonic  shell,  as  a  primitive 
Gastropod  shell  would  be  formed.  On  the  contrary,  the 
mantle  at  first  consists  of  two  folds  which  in  the  process 
of  development  come  together  on  the  ventral  side  and 

1  Proc.  Acad.  Nat.  Sci.  Phila.,  1899,  P-  52°- 

2Zool.  Anz.,  XXIII,  1900;  quoted  in  Science,  n.  s.,  XII,  1900, 
p.  824. 


METAZOA MOLLUSCA.  237 

make  a  tube  with  an  opening  at  each  end.  The  shell 
formed  by  the  mantle  grows  in  the  same  way,  and  is  a 
tube  open  at  either  end.  No.  534  (D.  entalis  Linn.), 
shows  the  animal  within  the  tube.  From  the  larger  or 
anterior  end  the  foot  projects.  The  mouth  with  the 
odontophore  is  at  the  base  of  the  foot. 

Plate  535  represents  the  fleshy  animal  as  taken  from 
the  shell;  fig.  i,  dorsal  view,  fig.  2,  ventral,  and  fig  3,  lat- 
eral view.  The  organ  colored  dark  green  in  the  model 
(No.  536)  is  the  liver;  the  kidney  is  at  the  forward  end 
of  the  liver,  while  the  generative  organs  are  on  one  side 
and  are  colored  yellow.  . 


HETEROPODA. 

In  the  Heteropoda  the  foot  is  modified  in  different  ways, 
sometimes  being  in  the  form  of  a  vertical  fin  extending 
from  the  ventral  side.  The  variability  of  the  gills  is 
shown  by  the  fact  that  in  this  group  they  are  present  or 
absent  in  species  of  the  same  genus  and  even  in  speci- 
mens of  the  same  species.1 

Atlanta  peroni  Les.  (No.  537),  has  a  glassy  shell  which 
is  a  vertical  spiral  in  the  young  animal,  but  which  later  be- 
comes flattened  in  one  plane.  The  last  whorl  increases 
rapidly  in  size,  and  the  aperture  is  flaring.  The  fleshy 
body  takes  the  coiled  spiral  form  of  the  shell  and  can  be 
wholly  drawn  into  it  and  protected  by  the  operculum. 
Around  the  outside  of  the  shell  there  is  a  thin  sharp  keel 
which  looks  at  first  glance  like  a  delicate  membrane. 

Carinaria  cristata  has  a  smooth  coiled  shell  when 
young  (PI.  538,  fig.  i,  left  side;  fig.  2,  right  side;  en- 
larged). When  older  the  shell  takes  the  form  of  a  coni- 
cal cap,  seen  in  fig.  3,  with  flutings  on  the  outer  surface. 
No.  539  is  the  shell  of  the  adult  of  another  species,  C. 

1  Tryon,  Structural  and  Systematic  Conchology,  II,  1883,  p-348. 


238  SYNOPTIC   COLLECTION. 

lamarcki  P.  &  L.,  in  which  the  early  tendency  to  coiling 
is  seen  at  the  apex,  while  No.  540,  C.  cithara  Bens.,  is 
suggestive  only  of  the  cap-like  form.  No.  541  is  the 
fleshy  animal  (C.  mediterranea),  and  PI.  542,  a  drawing  of 
C.fragilis  Bory.  It  is  drawn  with  the  ventral  side  upper- 
most, the  position  it  often  takes  in  swimming.  The  body 
is  long  and  the  leaf-like  fin  (see  No.  541)  which  is  a  modi- 
fied foot  is  seen  above,  while  below,  the  visceral  mass  con- 
sisting of  liver,  kidney,  heart,  reproductive  organs,  etc., 
is  reduced  in  size  and  covered  by  the  small  shell  (No. 

540- 

The  more  specialized   Heteropods  are  represented  by 

Pterotrachea  (No.  543,  P.  mutica-,  No.  544,  P.  coronata\ 
see  lowest  shelf)  in  which  the  body  has  lost  its  spiral 
form  and  become  cylindrical,  while  the  shell  has  wholly 
disappeared.  The  tentacles  are  also  lost  and  the  gills 
exist  only  as  vestiges. 


PTEROPODA. 

Recent  researches  point  to  the  conclusion  that  the 
ancestors  of  our  present  Pteropods  existed  in  the  early 
Palaeozoic  times. 

A  near  ally  of  Tentaculites,  Orygoceras  (PL  545,  fig.  i, 
O.  dentaliforme  ?),  had  a  plain  unornamented  shell.  The 
protoconch  is  not  represented  in  the  figures  of  this  spe- 
cies, but  is  finely  shown  in  O.  cornucopia*  (PL  545,  fig.  2). 
Succeeding  the  protoconch  the  young  shell  of  this  species 
is  seen  to  be  unornamented  like  the  adult  (fig.  i).  As 
the  animal  grows  older  the  shell  becomes  ridged  by  many 
circular  rings  (fig.  2). 

Tentaculites  (No.  546,  T.  gyr acanthus  Eaton;  PL  547, 
T.  acuarius  Richt.),  has  a  straight,  cone-shaped  shell  like 
that  of  Orygoceras,  with  a  simple  circular  aperture,  and 
with  concentric  ridges  of  rings  extending  around  the  out- 
side. These  ridges  are  carried  back  nearly  to  the  proto- 


METAZOA  —  MOLLUSCA.  239 

conch  by  the  law  of  acceleration  in  development,  so  that 
Tentaculites  comes  naturally  after  Orygoceras  in  our 
classification. 

Hyolithes  (No.  548,  H.  primordialis  Hall),  is  usually 
straight,  but  sometimes  curved.  Its  aperture  is  triangular 
and  is  provided  with  an  operculum.  The  shell  is  divided 
off  in  the  interior  by  horizontal  partitions. 

Conularia  (No.  549,  C.  congregata  Hall),  has  a  very 
thin  straight  shell  with  a  four-sided  aperture.  According 
to  Ruedemann1  Conularia  is  at  times  a  sessile  form  and 
is  found  attached  to  older  individuals  (PI.  550,  fig.  i,  C. 
gracilis  Hall,  x  2)  or  sometimes  to  foreign  objects.  PI. 
550,  fig.  2,  exhibits  the  young  of  different  ages  attached. 

The  full  and  beautiful  researches  of  Fol2  upon  Ptero- 
pods  have  given  us  much  knowledge  concerning  the  life 
histories  of  these  interesting  animals  as  well  as  their 
habits  and  structure. 

The  eggs  of  most  species  are  laid  at  the  going  down 
of  the  sun,  and  the  number  produced  by  one  individual  is 
enormous. 

When  the  Pteropod  embryo  of  to-day  leaves  the  egg  it 
possesses  a  shell  and  a  velum.  In  some  genera  the  shell 
is  present  throughout  life,  while  in  others  it  is  possessed 
by  the  larva  only.  The  velum  disappears,  and  the  foot 
changes  from  a  creeping  to  a  swimming  organ  by  devel- 
oping two  broad  lateral  expansions  usually  called  wings, 
but  which  are  really  oar-like  fins.  According  to  Pelsen- 
eer  these  little  creatures  swim  in  a  nearly  vertical  posi- 
tion with  the  head  uppermost  or  slightly  sloping,  so  that 
the  foot  is  turned  upward,  while  the  fins  move  backward 
and  forward. 

The  division  of  the  group  into  Thecosomata  and  Gym- 
nosomata  is  in  accordance  with  the  principle  of  a  natural 
classification. 


1  Amer.  Geol.,  XVII,  XVIII,  1896. 

2  Arch.  d.  Zooi.  Exper.  et  Gen.,  IV,  1875. 


240  SYNOPTIC    COLLECTION. 

Pelseneer,  who  has  made  a  special  study  of  the  anat- 
omy of  these  forms,  admits  that  "the  division  established 
on  the  very  empirical  character  of  the  presence  or  the 
absence  of  a  shell,  is  quite  justified  by  the  anatomical 
differences."1 

Thecosomata.  The  Thecosomata  are  among  the  more 
primitive  forms.  They  possess  a  shell,  and  the  animal 
adds  new  layers  to  it  as  it  grows.  The  head  is  indistinct 
and  the  wing-like  organs  extend  from  it  on  either  side 
and  are  joined  at  the  anterior  edge  above  the  mouth. 
The  anus  is  on  the  left  side. 

It  may  be  that  there  are  primitive  forms  among  the 
straight,  cone-shaped  Pteropods  living  to-day,  but  judging 
from  our  present  knowledge  of  the  anatomy  of  these 
straight  forms,  one  must  consider  them  as  secondary  and 
specialized  members  of  the  Pteropod  group,  and  the  spiral 
forms  living  to-day  as  the  more  generalized. 

The  spiral  condition  is  represented  by  Spirialis  aus- 
tralis  Soul.  (No.  551;  PL  552).  Its  tiny  spiral  shell 
protects  a  spirally  twisted  body  and  the  aperture  is 
closed  by  an  operculum. 

Spirialis  rostralis  Soul.  (No.  553  ;  PI.  554),  has  a  nauti- 
loid  shell  with  an  umbilicus.  The  figures  exhibit  the 
forward  part  of  the  body  with  its  appendages,  the  ex- 
panded wings,  and  the  viscera  enclosed  by  the  mantle. 

Creseis  aticula  Rang  (No.  555,  alcoholic  specimen ; 
Nos.  556,  557,  shells;  PI.  558,  figure  of  animal  in  shell), 
is  provided  when  young  like  all  Pteropods  with  a  shell 
formed  by  the  everted  shell  gland.  In  most  members  of 
the  group  this  shell  disappears  and  a  secondary  shell  is 
formed.  In  Creseis,  however,  the  primitive  and  second- 
ary shells  are  both  retained  throughout  life.  The  adult 
shell  is  smooth,  cone-shaped,  and  bilaterally  symmetrical, 
with  a  simple  aperture. 

It  would  seem  that  this  bilateral  symmetry  was  evi-. 

1  Chall.  Rep.,  Zoo!.,  XIX,  part  I,  1887,  p.  i. 


METAZOA  —  MOLLUSCA.  241 

dence  of  a  primitive  condition,  but  the  asymmetry  of  the 
internal  organs  proves,  as  already  pointed  out,  that  these 
forms  have  descended  from  spiral,  asymmetrical  Ptero- 
pods.  The  shell  has  become  adapted  for  swimming, 
while  the  internal  organs  have  not  been  so  modified. 
To  strengthen  these  views  there  are  species  of  these 
usually  straight  forms  which  have  the  protoconch  coiled 
dorsally,  indicating  a  former  coiled  condition.1  This 
genus  exhibits  the  cone-in-cone  structure  plainly  seen  in 
Creseis  striata  Rang  (No.  559  ;  PI.  560),  which  is  large 
and  finely  striated  on  the  outside.  This  straight  cone 
may  sometimes  in  the  same  species  become  horn-shaped, 
as  seen  in  PL  560. 

Cuvieria  columnella  Rang  is  like  Creseis  when  a  larva. 
No.  561  is  a  very  rare  specimen  in  which  the  small  cone- 
shaped  young  is  seen  preserved.  When  older  the  animal 
builds  a  transverse  partition  across  the  slender  tube,  then 
advances  and  makes  a  much  larger  tube  (No.  562).  The 
young  shell  is  usually  broken  off,  so  that  only  the  part 
built  by  the  adult  is  seen  (PI.  563).' 

Cymbulia  peroni  Cuv.  (No.  564,  animal;  No.  565, 
model ;  PL  566),  is  a  recent  form,  and  has  an  external, 
spiral,  operculated  shell  when  a  larva.  This  is  thrown 
off  and  a  secondary  shell  forms  which  is  also  cast  aside. 
Finally  in  some  species  an  internal  cartilaginous  shell  is 
produced  which  is  retained  throughout  life.  The  figure 
on  the  left  in  PL  566  is  a  view  of  the  shell  of  Cymbulia 
from  above  with  the  wings  expanded,  and  the  figure  on 
the  right  a  side  view  showing  the  slipper-like  form  of  the 
shell  and  the  position  of  the  animal  within  it.  The 
model  (No.  565)  represents  the  adult  with  its  delicate 
wings  spread.  Tiedemannia  neapolitana  (No.  567)  is  a 
nearly  related  genus  with  an  internal  shell. 

The  shell  of  Hyalea  is  essentially  a  hollow  cone.     The 

1  Chall.  Rep.,  ZooL,  XXIII,  Rep.  on  Pteropods,  part  3,  1888, 
p.  36. 


242  SYNOPTIC    COLLECTION. 

illustration  shows  the  exquisite  delicacy  of  Hyalea  globu- 
losa  Rang  with  its  blue  shell  and  softly  tinted  wings.  In 
this  species  the  shell  (No.  568)  is  nearly  globular  with 
the  dorsal  part  projecting  in  front  (PI.  569)  and  the  ven- 
tral part  convex. 

Hyalea  tridentata  Lam.  (No.  570),  is  a  much  larger 
species  with  a  golden  shell  (No.  571)  and  purple  and 
golden  wings  (PL  572).  The  upper  and  lower  parts  of 
the  shell,  and  the  open  spaces  between  the  two  are  seen 
in  the  side  view  (PI.  572,  figure  on  the  right). 

Cleodora  cuspidata  Bosc.  is  protected  by  a  glassy,  nearly 
transparent  shell  (No.  573)  with  three  projecting  spikes. 
The  visceral  mass  is  colored  in  the  figure  (PI.  574),  while 
the  other  parts  are  nearly  colorless.  The  alcoholic  speci- 
mens (No.  575)  show  different  ages  of  another  species, 
Cleodora  pyramidata. 

Balantium  recurvum  Child  (No.  576),  is  one  of  the 
larger  Pteropods.  Its  shell  is  triangular  in  shape  and 
terminates  in  a  sharp  point.  Its  delicate  coloring  and 
symmetrical  transverse  markings  make  it  a  beautiful 
object. 

Gymnosomata.  The  larva  of  Clio,  a  member  of  the 
Gymnosomata,  loses  its  primitive  and  secondary  shell  and 
its  velum  after  which  a  second  larval  form  appears  with 
three  bands  of  cilia  encircling  its  body.  This  second 
larva  is  without  a  mantle  and  secretes  no  shell. 

The  adult  (No.  577,  alcoholic  specimen  ;  PL  578,  Clio 
(  =  Clione)  borealis  Pe'ron)  has  a  long  body  with  a  distinct 
head.  The  latter  bears  two  pairs  of  tentacles  which  are 
provided  with  a  vast  number  of  tiny  suckers.  The  wings 
are  distinct  from  the  head  and  do  not  join  in  front,  in 
which  particulars  the  Gymnosomata  differ  from  the  The- 
cosomata.  The  foot  is  also  distinct  from  the  wings  and 
consists  of  a  posterior  lobe  with  two  smaller  anterior  ones. 
In  all  these  forms  the  anus  is  on  the  right  instead  of  the 
left  side  of  the  body. 

Pneumodermon  peroni  Q.  &  G.  loses  its  mantle  and  shell 


METAZOA MOLLUSCA.  243 

like  Clio  (No.  577)  and  moves  by  means  of  bands  of  cilia. 
The  adult  (No.  579,  No.  580,  P.  violaceum  d'Orb.),  pos- 
sesses a  distinct  head  which  carries  specialized  tentacles 
having  suckers  similar  to  those  of  cuttlefishes.  At  the 
posterior  end  of  the  body  there  are  external  gills  (No. 
58o). 

Clionopsis  krohni  (No.  581;  No.  582,  C.  flavescens 
Gegenbaur)  has  a  barrel-shaped,  shell-less  body  which 
is  nearly  transparent,  and  the  visceral  mass  extends  to 
the  posterior  end.  The  head  is  small  with  no  mouth 
appendages. 

Section  10. —  CEPHALOPODA. 

The  Cephalopoda  and  Brachiopoda  are  perhaps  the  best 
groups  that  can  be  chosen  at  the  present  time  to  illustrate 
a  natural  classification  based  upon  the  stages  of  growth 
and  decline.  It  is  obviously  impossible  to  follow  out  this 
classification  in  detail,  to  trace  the  numerous  branches  of 
the  Cephalopod  trunk  to  say  nothing  of  the  minute  twig- 
like  divisions  and  subdivisions  of  these  branches.  It  is 
hoped ,  however,  that  such  a  series  of  specimens  and  draw- 
ings has  been  selected,  and  such  an  arrangement  of  these 
made,  as  will  give  the  student  a  clear  general  view  of  the 
subject. 

It  is  well  to  impress  upon  one's  mind  at  the  very  out- 
set the  truth  of  the  words:  "A  single  shell,  either  from  a 
living  or  fossil  form,  may  present,  accurately,  the  general 
history  of  the  development  of  the  young,  the  stages  of  the 
adult  and  of  old  age." 1 

1  Hyatt,    Fossil    Cephalopods   in    the  Museum    of    Comparative 
Zoology,  Proc.  Amer.  Assoc.  Adv.  Sci.,  XXXII,  1883,  p.  323. 


244  SYNOPTIC    COLLECTION. 


TETRABRANCHIATA.  —  NAUTILOIDEA. 

When  the  Nautiloidea  first  appear  in  the  Palaeozoic 
strata  they  are  specialized  in  so  many  ways,  the  inference 
may  be  drawn  that  we  are  ignorant  of  the  radical  stock 
from  which  all  the  Cephalopods  have  descended.  A  study 
of  the  embryological  and  larval  structure  of  living  Nauti- 
loids,  however,  leads  to  the  conclusion  that  Diphragmo- 
ceras,  Piloceras  (PI.  583),  and  Endoceras  (No.  584)  are 
among  the  generalized  ancestors  of  the  group.  A  knowl- 
edge of  these  genera  and  of  the  Orthoceratites,  soon  to  be 
described,  enables  one  to  give  an  hypothetical  ancestral 
form  with  a  great  degree  of  certainty. 

Diphragmoceras  is  a  nearly  straight  tube  divided  into 
a  few  chambers  by  simple  plain  partitions  or  septa. 
Through  these  septa  runs  a  large  tube  or  siphuncle  which 
is  divided  by  septa  similar  to  those  in  the  surrounding 
shell.  The  structure  of  the  siphuncle  is  an  important 
character  in  the  classification  of  the  Nautiloids,  primitive 
forms  and  the  young  of  specialized  genera  having  large 
siphuncles,  while  those  of  adult  specialized  forms  are  small 
and  contracted.1 

Unfortunately  the  young  Piloceras  has  not  been  de- 
scribed. The  adult  is  both  straight  (PL  583)  and  curved. 
It  is  divided  by  septa  and  has  a  large  siphuncle.  Near 
the  apex  the  siphuncle  exhibits  a  cone-in-cone  structure 
which  is  more  developed  in  Endoceras.  The  latter  genus, 
when  young,  may  represent  the  full  grown  Piloceras. 
The  adult  Endoceras  (No.  584;  PI.  585,  vertical  section 
of  E.  proteiforme  Hall,  greatly  reduced),  is  a  straight  form 
with  a  shell  divided  into  chambers  by  septa.  Each  septum 
extends  downward  beyond  the  one  next  below,  forming 
funnels  which  taken  together  make  a  complete  siphun- 
cle (see  PI.  585).  This  tube  is  large,  being  sometimes 

1  See  Hyatt,  Proc.  Amer.  Assoc.  Adv.  Sci.,  XLVII,  1898,  p.  363. 


METAZOA  —  MOLLUSCA.  245 

more  than  one  half  the  diameter  of  the  shell.  Within  the 
siphuncle  are  cones,  one  within  another,  which  are  much 
more  plainly  seen  than  in  Piloceras.  To  understand  this 
structure,  one  must  consider  the  fleshy  body  of  the  animal. 
This  occupied  the  outermost  chamber  of  the  shell. 
Extending  backward  a  considerable  distance  from  its  pos- 
terior part  was  a  bag-like  prolongation  which  secreted 
shell  in  the  form  of  a  cone.  At  certain  periods  the  body 
advanced  and  while  resting  built  another  cone,  thus 
giving  rise  to  the  cone-in-cone  structure  seen  in  PI.  585. 
Extending  from  the  spire  of  the  cones  backward  to  the 
apex  of  the  shell  was  a  hollow  tube,  the  endosiphuncle, 
also  plainly  seen  in  PI.  585. 

Diphragmoceras,  Piloceras,  and  Endoceras  represent 
generalized  forms  having  huge  siphuncles.  These  be- 
come only  slightly  contracted  in  later  stages  of  growth. 
In  fact  the  generalized  members  of  this  class  do  not  pass 
through  marked  changes  in  external  form  and  ornamenta- 
tion or  in  internal  structure  ;  one  genus,  Cyrtocerina,  proba- 
bly preserving  its  large  siphuncle  unchanged  throughout 
life.1 

Much  more  is  known  of  the  young  of  the  genus  Ortho- 
ceras  than  of  the  preceding  genera.  Its  protoconch  has 
been  observed.  Figs.  1-3  of  PI.  586  represent  the  proto- 
conch of  Orthoceras  elegans  Munst,  from  the  front,  side, 
and  above  ;  (a)  protoconch,  (b)  shell ;  figs.  4-6,  the  proto- 
conch of  Spyroceras  (=  Orthoceras)  crotalum  Hall.  This 
protoconch  is  a  chamberless,  septa-less  shell,  usually  very 
much  shrunken  owing  to  the  delicate  substance  —  conchi- 
olin  — of  which  it  was  made.  Here  we  have  a  clew  to  the 
radical  form  that  gave  rise  to  the  Cephalopods,  and  proba- 
bly to  the  Gastropods  and  Pteropods  as  well. 

In  figs.  4-6  not  only  is  the  protoconch  distinctly  seen 
but  also  the  different  substages  of  the  nepionic  stage. 

1  Hyatt,  Genesis  of  the  Arietidae,  Smithsonian  Contrib.  to  Knowl- 
edge, XXVI,  1889,  p.  39. 


246  SYNOPTIC    COLLECTION. 

The  markings  of  the  protoconch  are  carried  over  contin- 
uously to  the  beginning  of  the  nepionic  stage,  proving 
conclusively  that  the  shell  or  conch  was  formed  on  the 
edges  of  the  protoconch.  Usually  the  protoconch  is 
broken  off  and  in  these  cases  a  scar  is  left.  Fig.  7  (O. 
unguis)  shows  the  scar  and  the  conch  of  the  apex.  Fig. 
8  is  a  view  of  the  apex  of  the  same  species  after  the  proto- 
conch has  been  accidentally  broken  off,  fracturing  the 
outer  shell  and  exposing  the  scar. 

The  young  has  a  large  siphuncle  which  afterwards  in 
the  process  of  growth  becomes  contracted,  but  never 
develops  the  cone-in-cone  structure,  or  an  endosiphuncle. 
This  tends  to  prove  that  Orthoceras  descended  from 
forms  with  a  large  siphuncle  and  that  the  small  siphuncle 
is  a  secondary  condition. 

The  position  of  the  siphuncle  is  usually  near  the  center 
of  the  septa,  as  seen  in  No.  587,  which  represents  a  portion 
of  the  adult  shell.  The  septa  are  plain  and  concave 
towards  the  living  chamber.  The  shell  is  straight  and 
unornamented,  with  a  simple  aperture.  It  is  marked  by 
that  genuine  simplicity  which  characterizes  primitive 
forms. 

The  tendency  of  the  primitive  straight  shell  to  become 
coiled  is  shown  in  Cyrtoceras  and  Gyroceras.  Cyrtoceras 
(PI.  588)  is  more  or  less  curved,  but  is  never  coiled.  The 
septa  are  concave  towards  the  forward  part,  the  aperture 
is  large,  and  the  ventral  sinus  is  distinct.  In  Gyroceras 
(PI.  589)  the  process  of  coiling  begins,  but  the  whorls  are 
not  in  contact,  so  that  the  result  is  a  loose  spiral.  The 
aperture  is  simple  and  the  septa  are  plain  and  concave. 

There  are  fossil  forms  among  the  Nautiloids  in  which 
the  whorls  are  closely  coiled,  as  in  Nautilus  dekayi  Mor- 
ten (No.  590,  showing  septa  and  siphuncle)  and  Nautilus 
intermedius  Sow.  (No.  591).  In  some  species  these  whorls 
are  visible  (No.  591  ;  No.  592,  Nautilus  umbilicatus  Lis- 
ter; section  of  shell),  and  in  consequence  of  this  mode  of 
growth  the  species  has  a  deep  umbilicus  on  either  side. 


METAZOA  —  MOLLUSCA.  247 

The  tendency  .towards  becoming  an  involute  shell  is 
seen  in  Nautilus  stenomphalus  Sow.  (Nos.  593,  594). 
The  involute  shell  in  which  the  earlier  whorls  are  entirely 
concealed  by  the  latest  whorl  is  seen  in  Nautilus pompi- 
lius  Linn.  (PI.  595  ;  Nos.  596,  597).  The  development 
of  this  species  is  extremely  interesting  from  a  phylo- 
genetic  point  of  view.  The  first  chamber  of  the  shell  of 
the  young  Nautilus  has  a  linear  scar  (PI.  595,  fig.  2) 
which  probably  marks  the  spot  where  the  protoconch  was 
broken  off.  The  protoconch  itself  has  never  been  found 
in  perfect  condition  in  this  group,  though  the  scar  bears 
strong  evidence  of  its  former  existence.  There  are  good 
reasons  why  the  protoconch  of  Nautilus  should  be  lost. 
It  was  probably  made  of  frail  material  which  would  easily 
be  broken  while  the  animal  was  swimming  about  in  the 
sea.  Then  again,  when  the  young,  nearly  straight  shell 
began  to  coil,  the  hard  calcareous  first  whorl  would  come 
so  close  to  the  delicate  protoconch  that  the  latter  could 
hardly  fail  to  be  destroyed.  The  protoconch  was  doubt- 
less connected  with  the  first  chamber  by  an  'opening 
which  is  plugged  up  in  the  present  Nautili,  the  scar  mark- 
ing its  position. 

In  a  section  through  a  young  shell  of  Nautilus  pompi- 
lius  Linn.  (PI.  595,  fig.  i),  the  first  living  chamber  is 
almost  straight,  while  the  rest  is  slightly  curved.  This 
chamber  was  occupied  by  the  young  animal  after  the  pro- 
toconch stage.  It  was  septa-less  like  the  protoconch  and 
without  a  siphuncle.  In  course  of  time  the  animal  ad- 
vanced and  made  a  wall  or  septum  behind  it.  This  sep- 
tum bent  downward  into  the  first  chamber  forming  a 
coecum  or  the  beginning  of  the  siphuncle  as  seen  in  the 
figure.  The  second  septum  likewise  is  prolonged,  and  its 
coecum  extends  downward  into  the  first  coecum.  the  bot- 
tom of  the  coecum  forming  a  septum  across  the  siphuncle. 
This  early  condition  of  Nautilus  represents  the  adult  Di- 
phragmoceras  with  its  large  septate  siphuncle. 

The  third  septum  in  Nautilus  extends  only  to  the  sec- 


248  SYNOPTIC    COLLECTION. 

ond  septum,  forming  a  long  funnel  with  no  septum  at  the 
bottom.  The  siphuncle  begins  to  contract  and  from  this 
time  on  is  without  septa,  resembling  the  contracted  septa- 
less  siphuncle  of  Orthoceras  which  arises  in  the  same 
way ;  i.  e.,  by  the  formation  of  long  funnels. 

Fig.  2  represents  the  nepionic  stage  of  Nautilus  as  seen 
from  the  front.  The  specimen  has  been  obtained  by 
breaking  down  a  full  grown  shell.  The  vertical  scar 
marking  the  position  of  the  protoconch  is  distinct,  while 
the  circular  siphuncle  is  of  large  size.  Fig.  3  is  the  same 
seen  from  the  side.  It  shows  the  increase  in  ornamenta- 
tion from  a  comparatively  smooth  shell.  The  lines  of 
growth  do  not  bend  backward  in  the  middle  of  the  ven- 
tral side  but  run  nearly  straight. 

Fig.  4  shows  finely  the  scar  and  the  area  of  attachment 
of  the  protoconch  ;  the  siphuncle  and  first  few  septa  are 
also  plainly  visible.  The  adult  Nautilus  is  represented 
by  No.  596,  the  shell ;  and  No.  597,  a  section  showing  an 
alcoholic  specimen  of  the  fleshy  animal  within  its  shell. 

The  involute  spiral  form  has  been  attained  and  the 
coiling  has  taken  place  in  such  a  way  that  the  ventral 
convex  side  is  outermost  and  the  concave  dorsal  side 
innermost.  As  the  shell  coiled,  the  newly  formed,  more 
or  less  plastic  whorl  came  in  contact  with,  and  was  pressed 
by  the  harder  and  older  preceding  whorl.  The  tighter 
the  coiling  the  deeper  we  should  say  would  be  the  impres- 
sion. This  impressed  area  in  the  dorsal  side  of  the  shell 
is  known  as  the  impressed  zone,  and  is  an  important 
character  in  both  Nautiloids  and  Ammonoids. 

In  the  adult  Nautilus  the  septa  extend  backward  only 
a  short  distance,  giving  rise  to  short  funnels  in  place  of 
the  long  ones  of  more  generalized  forms.  These  funnels 
are  connected  by  a  porous  tube  secreted  by  the  siphon, 
and  the  two  taken  together  form  the  siphuncle.  This  is 
well  seen  in  the  section  of  the  shell  (Nos.  592,  597)  run- 
ning from  the  outermost  chamber  to  the  innermost.  Its 
position  is  near  the  center  of  the  concave  septa.  It  will 


METAZOA  MOLLUSCA.  249 

be  observed  that  the  septa  are  much  nearer  together  in 
the  adult  than  in  the  young  (PI.  595,  fig.  i).  If  a  sec- 
tion of  an  old  shell  is  examined  the  septa  are  sometimes 
found  even  nearer  together  than  in  the  ephebic  stage. 
This  is  especially  interesting  and  exceptional,  since  just 
the  opposite  condition  of  things  exists  in  the  old  age  or 
gerontic  stage  from  what  has  been  described  in  the  young 
stage. 

A  study  of  the  young  and  the  adult  shell  leads  to  a 
study  of  the  fleshy  parts  of  the  animal.  No.  597  is  an 
alcoholic  specimen  of  the  Nautilus.  It  is  placed  in  its 
natural  position  with  the  ventral  side  below.  The  large 
head  and  body  of  the  animal  occupy  the  outer  chamber 
of  the  shell,  and  the  long  fleshy  tube  or  siphon  extends 
from  the  posterior  part  of  the  body  backward  to  the  inner- 
most chamber.  It  is  supposed  by  some  that  the  cham- 
bers of  the  shell  are  supplied  with  gas  and  by  others  with 
liquid.  On  the  ventral  side  the  two  flaps  of  the  mantle 
have  united,  forming  an  ambulatory  pipe  or  hyponome 
by  means  of  which  the  animal  is  propelled  through  the 
water.  The  motions  of  this  organ  have  caused  a  sinus 
in  the  aperture  of  the  shell  (see  Nos.  592-594,  596),  and 
the  additional  layers  made  to  the  shell,  indicated  by  the 
lines  of  growth,  bend  backward  running  parallel  with  this 
sinus.  As  we  have  already  said,  no  sinus  occurs  in  the 
young  Nautilus,  so  that  probably  at  this  stage  it  is  not 
a  swimming  animal.  The  mouth  of  the  creature  is  sur- 
rounded by  arms  for  obtaining  food,  but  these  are  with- 
out sucking  cups. 

The  edges  of  the  mantle  make  the  shell  already  de- 
scribed, while  the  mantle  on  the  posterior  part  of  the 
body  builds  the  septa  during  periods  of  rest.  The  short 
funnels  of  the  siphuncle  are  made  by  the  mantle,  while 
the  siphon  secretes  the  porous  wall  which  connects  the 
funnels  together. 

In  the  group  of  Nautiloids  there  is  no  straight  old  age 
form,  the  involute  form  existing  at  the  present  time. 


250  SYNOPTIC    COLLECTION. 


AMMONOIDEA. 

There  are  sufficient  remnants  of  the  early  transitional 
forms  left  in  the  Silurian  rocks  to  demonstrate  the  former 
connection  of  the  Nautiloids  and  the  Ammonoids.1  The 
common  ancestor  for  the  two  groups  probably  existed  in 
pre-Cambrian  times,  but  this  form  has  not  been  discov- 
ered. Clarke2  has  described  an  Orthoceras-like  form 
from  the  Devonian.  It  has  a  large,  plump  protoconch 
(PI.  598,  fig.  i)  like  that  of  Ammonoids,  but  the  central 
position  of  the  siphuncle  (fig.  2)  is  like  that  of  Orthoceras. 
According  to  Clarke  this  protoconch  was  probably  de- 
rived from  so  young  a  shell  that  atrophy  and  wrinkling 
had  not  taken  place,  as  is  the  case  with  the  mature  Ortho- 
ceran  shells,  all  of  which  have  been  found  in  a  later  geo- 
logic formation.  The  connection  of  the  protoconch  with 
the  conch  is  seen  to  be  large,  which  is  the  case  with  the 
generalized  Ammonoids,  while  it  is  narrow  in  the  Nauti- 
loids, as  seen  in  PI.  586. 

Bactrites  is  probably  the  primitive  straight  form  from 
which  the  Ammonoidea  arose.  The  protoconch  is  seen 
in  PI.  599,  fig.  i,  while  in  fig.  2  it  occurs  with  a  few 
chambers. 

When  this  protoconch  is  not  present,  the  apex  (fig.  3 ) 
is  marked  by  a  scar  (figs.  3,  4).  When  the  protoconch  is 
broken  off  the  opening  of  the  siphuncle  in  the  first  sep- 
tum (PI.  599,  fig.  5,  somewhat  broken),  is  seen  to  be  intra- 
marginal  instead  of  being  central  as  in  Orthoceras,  or 
marginal  as  in  typical  Ammonoids.  PI.  599,  fig.  6,  shows 
the  protoconch  and  the  enlargement  of  the  shell  which 
goes  on  until  two  chambers  have  been  formed,  after 
which  the  tube  contracts. 

An  older  specimen  is  figured  in  PI.  599,  fig.  7  (a  dorsal 


1  Hyatt,  Proc.  Amer.  Assoc.  Adv.  Sci.,  XXXII,  1883. 

2  Amer.  Geol.,  XII,  1893,  p.  112. 


METAZOA — MOLLUSC A.  251 

view  of  an  internal  cast),  showing  the  long  tube,  the 
slightly  oblique  sutures,  and  the  flaring  aperture.  As 
specimens  are  usually  preserved  the  siphuncle  appears  to 
be  distinctly  marginal,  but  Clarke  has  shown  that  this  is 
not  the  case,  but  that  a  narrow  portion  of  the  septum  lies 
between  the  siphonal  funnel  and  the  shell  wall.  This  is 
shown  in  fig.  8,  which  is  the  interior  of  a  portion  of  the 
shell  showing  the  intra-marginal  position  of  the  siphonal 
funnel. 

Mimoceras  (  =  Goniatites)  compressum  (PI.  600),  has  a 
protoconch  which  is  permanent  throughout  life.  This  is 
well  seen  in  figs.  1-3.  These  figures  show  that  the  shell 
is  nearly  straight  at  first,  and  that  the  septa,  and  therefore 
the  sutures,  are  primitive  and  similar  to  those  of  the  Nau- 
tiloidea.  The  septa  are,  in  fact,  concave  both  in  the 
young  and  in  the  adult.  The  siphuncle  is  nearer  the 
center  at  first  and  later  approaches  the  ventral  side. 
The  adolescent  shell  is  loosely  coiled  (fig.  3),  the  whorls 
not  being  in  contact.  Later,  however,  the  shell  becomes 
closely  coiled,  as  seen  in  figs.  4,  5  ;  also  figs.  6,  7  (M. 
ambigena).  Fig.  5  shows  the  older  septa  with  the 
siphonal  lobe.  The  outline  of  the  aperture  of  the  shell 
is  rounded  on  the  dorsal  as  well  as  the  ventral  side  (fig. 
7  ).  This  is  an  important  character  showing  the  absence 
of  an  impressed  zone  at  a  late  stage. 

In  these  generalized  forms  of  the  Ammonoidea,  signifi- 
cantly called  the  Nautilinidae,  the  Nautiloid  characters 
are  retained  for  a  considerable  length  of  time,  but  later 
new  structural  features  appear  which  are  distinctly  Am- 
monoidai. 

Adult  Goniatites  in  general  have  the  septa  concave  as 
in  the  Nautiloids,  but  the  sutures  though  simple  (No.  60 1, 
Brancoceras  ixion  Hyatt),  have  a  few  lobes  (backward 
bendings  of  the  septa)  and  saddles  (forward  bendings  of 
the  same  parts).  The  aperture  is  simple  with  ventral 
sinus  like  that  of  Nautilus.  The  siphuncle  is  at  first  cen- 
tral in  position  and  later  reaches  the  ventral  margin  where 


252  SYNOPTIC    COLLECTION. 

it  makes  a  siphuncle  lobe  (No.  601,  specimen  on  the 
right),  which  later  in  life  in  some  species  becomes  divided, 
giving  rise  to  the  siphuncle  saddle. 

The  Goniatites  cease  to  exist  in  the  Carboniferous  age 
and  the  Ceratites  appear.  The  specimen  of  Ceratites 
(No.  602,  C.  nodosus  De  H.),  does  not  show  the  younger 
whorls  but  the  sutures  of  the  last  whorl  are  finely  seen. 
The  number  of  saddles  and  lobes  has  increased  but  still 
can  be  easily  counted.  The  bottom  of  the  lobes  is  ser- 
rated, which  may  be  seen  in  several  places  in  the  speci- 
men. 

The  more  primitive  Ammonitidae  are  represented  by 
Deroceras  (=  Ammonites)  planicosta  Hyatt.  Here  the  pro- 
toconch  is  large  and  globular  (PI.  603,  fig.  i).  In  this 
figure  the  shell  is  seen  on  the  right  with  a  few  septa,  and 
on  the  left  it  is  broken  exposing  the  cast  of  the  proto- 
conch.  Fig.  2  is  a  section  of  the  same.  The  contraction 
of  the  siphuncle  is  well  seen.  Fig.  3  is  a  section  through 
the  shell  with  the  protoconch  broken  off.  The  coecum 
formed  by  the  first  septum  is  finely  shown  ;  three  other 
septa  are  drawn.  An  organic  deposit  fills  the  siphuncle. 
Fig.  4  is  a  section  through  the  shell  of  a  related  genus, 
Plenroceras  spinatum  Branco,  showing  the  protoconch  in 
the  center,  the  coecum  and  siphuncle,  the  first  concave 
Nautiloid  septum,  and  the  remaining  convex  Atnmonoidal 
septa.  It  is  interesting  to  know  that  the  septa  of  the  first 
formed  chambers  are  simply  curved,  while  in  the  adoles- 
cent stage  they  resemble  those  of  Goniatites,  having  few 
lobes  and  saddles  (see  fig.  5).  In  the  whorls  of  the  adult 
they  are  always  folded  (see  outer  whorl  in  fig.  5). 

In  this  adult  shell  the  ventral  sinus  of  the  aperture,  so 
conspicuous  in  the  Nautiloids,  has  disappeared  and  the 
lines  of  growth  are  continued  straight  across  the  ventral 
portion.  This  being  the  case  we  must  infer  that  the 
organ  which  caused  the  sinus  has  disappeared.  Hyatt1 

1  Genesis  of  the  Arietidae,  Smithsonian  Contrib.  to  Knowledge, 
XXVI,  1889. 


M  ETAZOA MOLLUSCA .  253 

has  pointed  out  that  this  change  in  structure  indicates 
a  change  in  habits  whereby  a  swimming  type  of  Cepha- 
lopod  has  been  converted  into  a  crawling  type. 

In  Dactylioceras  (No.  604,  D.  commune  Hyatt),  the 
whorls  are  closely  coiled  and  in  the  same  plane  ;  all  are 
visible  and  the  ornamentation  is  similar. 

These  characters  are  seen  on  a  large  scale  in  Ammo- 
nites parkinsoni  which,  on  account  of  its  size,  is  placed  at 
the  back  of  the  Section  (see  No.  605  ;  No.  606,  horizon- 
tal section  of  the  same).  A  portion  of  the  shell  has  been 
removed  in  No.  605,  and  the  surface  polished,  thereby 
bringing  out  the  sutures  finely.  In  No.  606  the  cham- 
bers and  their  walls  are  well  shown. 

Asteroceras  (  =  Ammonites,  also  =  Arietites)  obtusum 
Hyatt  (No.  607)  has  the  whorls  in  one  plane  and  all 
can  be  counted.  The  shell  is  tightly  coiled  and  even  the 
youngest  whorls  are  ornamented  with  ribs.  This  speci- 
men has  most  of  the  shell  well  preserved.  The  sutures 
are  hidden,  but  where  the  shell  is  broken  off  the  serrated 
or  fluted  edges  of  the  septa  are  visible  though  more  clearly 
seen  in  No.  608  where  the  outer  shell  is  entirely  gone. 
These  sutures  are  complex  as  compared  with  those  of 
Goniatites,  Ceratites,  or  the  primitive  Ammonites.  The 
siphuncle  is  seen  on  the  edge  and  the  specimen  also 
shows  how  the  dorsal  side  of  the  shell  has  become  im- 
pressed by  close  coiling.  The  living  chamber  extends 
backward  a  considerable  distance  (No.  608),  the  last 
formed  septum  marking  its  posterior  limit. 

The  complexity  of  the  septa  is  seen  in  Lytocera s  jurense 
Sitt.  (No.  609),  where  the  edges  of  the  septa  have  been 
painted  red  to  bring  out  their  structure  more  plainly. 

No.  6 10,  Stephanoceras  tarA^&xr/d'Orb.,  shows  the  tend- 
ency of  a  closely  coiled  shell  to  become  involute.  The 
last  whorl  spreads  out  laterally  and  partially  covers  the 
preceding  whorls,  leaving  a  deep  umbilicus  on  either  side. 
The  dorsum  is  deeply  impressed  in  this  genus.  Several 
of  the  specimens  in  No.  608  have  a  portion  of  the  exter- 


254  SYNOPTIC    COLLECTION. 

nal  shell  preserved  which  exhibits  a  brilliant  iridescence. 
Where  the  shell  is  broken  the  septa  and  chambers  are 
visible.  The  middle  portion  of  the  septum  in  the  upper 
left  hand  specimen  is  seen  to  be  nearly  flat  but  the  edges 
are  deeply  fluted.  In  the  largest  specimen  on  the  right, 
the  shell  is  mostly  worn  away,  revealing  the  complex 
character  of  the  sutures. 

No.  611,  Perisphinctes,  belongs  to  another  series  in 
which  the  shell  is  compressed,  but  the  younger  whorls 
are  not  covered.  The  marginal  siphuncle  and  the  fluted 
sutures  are  remarkably  well  seen  in  this  specimen.  An- 
other species  of  this  genus,  No.  612,  P.  comptoni  Pratt, 
has  long  lateral  processes  or  ears  extending  from  the  liv- 
ing chamber. 

Phylloceras  heterophyllum  Suss.  (No.  613).  is  not  only 
compressed  but  involute.  The  shell  has  mostly  disap- 
peared, revealing  the  extremely  complex  character  of  the 
sutures.  The  section  shows  the  protoconch  in  the  cen- 
ter, the  closely  coiled  young  shell,  the  septa,  and  the 
chambers  filled  with  mineral  matter.  As  might  be  ex- 
pected these  extremely  specialized  Ammonites  are  not 
found  in  the  ancient  Palaeozoic  strata  but  occur  in  the 
Mesozoic  formations. 

Aturia  zizac  Sow.  is  found  in  the  recent  Tertiary  rocks, 
and  is  a  compressed,  involute  form  with  specialized 
sutures,  and  differentiated,  nearly  dorsal  siphuncle  (No. 
614;  also  PI.  615,  figs.  1-3).  Growth  in  this  genus  is 
very  rapid  during  the  nepionic  stage,  the  coiling  is  close, 
and  the  funnels  of  the  siphuncle  are  flaring  (see  fig.  i). 
Fig.  2  is  a  front  view,  and  fig.  3  a  side  view  of  the  nepi- 
onic and  half  of  the  neanic  stages.  Fig.  2  shows  the 
nearly  dorsal  position  of  the  siphuncle,  and  fig.  3  the 
lobes  of  the  first  four  sutures.  No.  616,  Aturia  aturi 
Bast,  is  a  valuable  specimen  obtained  by  breaking  down 
the  shell  so  that  the  funnels  of  the  siphuncle  are  exposed. 

It  has  been  shown  that  the  Nautiloids  and  Ammonoids 
both  arose  from  straight  Orthoceras-like  shells,  and  in 


METAZOA MOLLUSCA.  255 

their  development  passed  through  the  loosely  coiled, 
tightly  coiled,  and  involute  stages.  The  Nautilus  was 
seen  to  be  an  involute  form,  but  no  reduced  stage  with 
a  more  or  less  uncoiled  spire  was  described  since  no  such 
form  has  been  discovered. 

Among  the  Ammonoids,  however,  a  number  of  series 
have  been  traced  from  the  straight  primitive  form  through 
the  involute  stages  to  the  straight  reduced  condition. 

The  Ammonites  culminated  in  the  Jurassic  period. 
At  the  close  of  this  period  in  all  probability  there  was 
some  great  climatic  change  which  caused  reduction.  The 
Nautiloids  were  somewhat  affected,  but  not  enough  to 
cause  them  to  become  extinct.  Those  that  died,  did  so 
slowly.  The  Ammonites,  on  the  contrary,  developed 
extraordinary  reduced  forms  and  afterwards  became  ex- 
tinct. 

The  first  indications  of  reduction  are  a  lateral  contrac- 
tion in  the  whorl  (see  No.  617,  Sphaeroceras  brochi  Sow.), 
attended  with  a  diminution  in  the  size  and  a  decrease  in 
the  vertical  height  (No.  618,  Sphaeroceras  wrighti}.  In 
some  cases  the  process  is  carried  so  far  that  the  terminal 
portion  of  the  last  whorl  separates  from  the  preceding 
whorls  and  grows  out  straight,  as  seen  in  Scaphites  nodo- 
sus  Meek.  The  young  Scaphites  (No.  619,  specimen  on 
the  left,  and  the  section,  No.  620)  are  closely  coiled,  but 
the  older  stage  (No.  619,  specimen  on  the  right)  has 
begun  to  uncoil.  This  is  still  better  seen  in  No.  621, 
which  is  a  cast  of  an  aged  specimen  of  Eurystomites  kel- 
loggi  showing  the  free  volution  or  whorl. 

Another  old  age  form  is  seen  in  No.  622,  Helicoceras 
stevensoni  Whitfield,  where  the  asymmetrical  spiral  has 
partly  uncoiled,  and  the  last  whorl  has  a  secondary  back- 
ward crook  bringing  the  aperture  of  the  shell  near  the 
base  of  the  spire. 

The  uncoiled  condition  is  carried  still  farther  in  Crio- 
ceras  bifurcatus  Quenst.  (No.  623),  in  which  the  shape 
is  more  like  a  hook  than  a  spiral. 


256  SYNOPTIC    COLLECTION. 

Finally,  the  straight  form  is  very  nearly  attained  in 
Baculites  (PI.  624,  figs,  i-io  ;  No.  625),  but  this  straight 
adult  Ammonite  has  a  tiny  coiled  shell  when  young.  It 
is  interesting  to  note  that  the  protoconch  has  become 
modified,  so  that  its  shape  is  suggestive  of  a  spiral  when 
seen  from  the  side  (PI.  624,  fig.  i).  The  typical  globu- 
lar form  has  become  broadly  elliptical  (fig.  2,  front  view) 
with  a  projection  extending  forward  (fig.  i).  . 

The  earliest  stage  of  the  larval  nepionic  shell  is  seen 
in  fig.  3.  An  older  shell  having  four  septa  shows  the 
siphuncle  near  the  center  (fig.  4).  The  aperture  at  this 
stage  is  broad,  and  the  area  of  contact  of  the  revolving 
whorl  upon  the  preceding  whorl  is  also  broad,  as  shown 
by  the  dotted  lines.  The  septa  at  first  are  simple.  Fig. 
5  represents  a  side  view  of  the  shell  with  six  septa,  and 
fig.  6  the  first  six  sutures.  Three  of  these  sutures  are 
simple,  while  the  remaining  three  are  similar  to  the 
sutures  of  Goniatites.  A  front  view  of  a  stage  with  thir- 
teen septa  (fig.  7)  shows  the  siphuncle  near  the  margin, 
the  aperture  and  area  of  contact  narrower  so  that  the 
growing  whorl  envelops  less  of  the  shell.  In  a  still  older 
stage  with  seventeen  septa  (fig.  8)  the  siphuncle  is  close 
to  the  edge,  the  aperture  is  almost  circular,  while  the  area 
of  contact  is  much  narrower,  as  indicated  by  the  dotted 
lines.  When  the  shell  has  the  diameter  of  one  millimeter 
and  consists  of  two  or  two  and  a  half  whorls  with  from 
twenty  to  twenty-five  septa  it  begins  to  grow  out  in  a 
straight  line.  Fig.  9  represents  the  adolescent  (neanic) 
shell  at  this  stage  with  the  lines  of  growth  and  the  ros- 
trum at  the  opening. 

The  sutures,  which  are  concealed  in  fig.  9,  become 
more  complex,  passing  from  the  Goniatite  condition  to 
the  Ceratite  (see  lower  suture  in  fig.  10)  at  about  the 
thirtieth  septum  or  after  the  shell  has  become  straight. 
After  this  the  lobes  and  saddles  increase  in  number  until 
the  extremely  complex  sutures  of  the  adult  Ammonite  are 
produced  (upper  sutures  in  fig.  10;  see  also  No.  625). 


METAZOA MOLLUSCA.  257 

In  the  history  of  the  development  of  Baculites  we  have 
positive  proof  of  the  reduced  character  of  the  genus.  In- 
stead of  being  a  relative  of  the  primitive  straight  Ortho- 
ceras  or  of  Bactrites,  it  is  an  extremely  specialized  form 
whose  ancestors  in  their  evolutionary  history  passed 
through  the  various  stages  of  shell  development.  Of 
these  stages  the  straight  and  loosely  coiled  stages  are 
omitted  in  Baculites,  so  that  the  animal  begins  life  with 
a  tightly  coiled  shell,  which,  however,  ceases  to  coil  in 
the  neanic  stage,  forming  thereafter  a  straight  cone. 


DlBRANCHIATA.  —  BfiLEMNITIDAE. 

The  Belemnitidae  begin  in  the  Triassic  period  and  are 
therefore  more  recent  than  the  Nautiloids  or  the  Am  mo- 
noids. We  should  expect  to  find  them  more  specialized 
though  still  retaining  certain  characters  of  their  ancestors. 

We  have  seen  in  Nautilus  the  dorsal  fold  of  the  mantle 
which  secretes  the  black  pigment  layer.  In  Aulacoceras 
(PL  626,  figs.  1-3,  A.  reticulatum  Hauer),  the  dorsal  fold 
was  nearly  closed  and  secreted  a  shell  with  three  princi- 
pal parts:  the  chambered  shell  or  phragmacone  (fig  i, 
ph)  ;  the  guard  (fig.  i,,^;  fig.  3),  and  a  prolongation  of 
the  phragmacone,  the  pro-ostracum  (see  upper  part  of  fig. 
i),  often  called  the  pen,  which  is  seldom  preserved.  The 
phragmacone  has  chambers,  septa,  and  siphuncle  (fig.  2, 
section).  It  corresponds  with  the  shell  of  the  Tetra- 
branchiata,  but  differs  from  the  latter  by  being  internal. 

The  more  specialized  form,  Belemnites  (No.  627),  has 
a  conical,  chambered  shell,  at  the  anterior  end  of  which 
on  the  dorsal  side  there  was  the  shovel-like  projection  or 
pro-ostracum.  The  septa  of  the  shell  were  plain  (No. 
627),  concave,  and  were  pierced  by  a  siphuncle  which 
does  not  show  in  the  specimen.  This  shell  is  external 
in  the  young  Belemnite.  In  time  the  dorsal  flap  of  the 
mantle  grows  out  and  around  the  shell,  its  two  edges  not 


258  SYNOPTIC    COLLECTION. 

meeting  ventrally  at  first,  but  eventually  coming  together 
and  joining.  When  this  has  happened,  the  mantle  makes 
the  first  layer  of  the  guard  (No.  627).  Successive  layers 
are  put  on  from  without,  thereby  illustrating  exogenous 
growth.  In  many  genera  the  guard  extends  a  consider- 
able distance  below  the  chambered  shell  and  is  the  part 
most  frequently  preserved  (see  No.  628,  B.  subquadratus 
Roem.). 

Thus  it  is  seen  that  Belemnites  carries  specialization 
so  far  that  the  shell  is  enclosed  and  a  secondary  struc- 
ture, the  guard,  is  formed. 

One  of  the  descendants  of  the  Belemnites  is  the  beauti- 
ful living  Spirula  (Nos.  629,  630)  which  has  lost  both  the 
pen  and  the  guard.  A  perfect  specimen  of  this  animal  is 
extremely  rare,1  but  the  alcoholic  specimen  (No.  629), 
though  mutilated,  shows  that  the  shell  is  partly  internal. 
It  also  exhibits  a  portion  of  the  mantle  and  what  some 
naturalists  consider  the  disc  of  attachment. 

The  shell  has  a  large,  globular  protoconch  finely  seen 
in  No.  630.  The  plain  concave  septa  are  pierced  by  the 
marginal  siphuncle  which  is  made  up  of  funnels  that 
extend  from  one  septum  to  another. 

Belosepia,  according  to  Zittel,  connects  the  Phragma- 
phora  (Belemnites,  Spirula,  etc.)  with  the  Sepiophora 
(cuttlefishes  and  squids).  It  has  a  guard  and  the 
chambered  shell  is  represented  indistinctly. 

The  young  cuttlefish  of  to-day,  Sepia  officinalis  Linn. 
(PL  631,  figs,  i,  2),  has  the  interesting  habit  of  fas- 
tening itself,  for  a  day  or  two  after  hatching,  by  a  portion 
of  the  lower  side  of  the  body  and  of  the  ventral  arms. 
This  sucker-like  area  is  flat  and  nearly  colorless,  and 
reminds  one  forcibly  of  the  foot  of  a  Gastropod.  Fig.  i 
is  a  view  of  the  animal  drawn  from  below  when  attached 
to  a  glass  plate ;  the  arms  are  retracted.  Fig.  2  is  from 

1  According  to  Pelseneer  (Nat.  Sci.,  VII,  1895,  p.  63)  only  five 
complete  specimens  are  known. 


METAZOA MOLLUSCA.  '259 

above  while  in  the  same  position.  The  line  between  the 
two  figures  represents  the  actual  length  of  the  animals. 

After  detaching  itself,  the  young  Sepia  swims  by  means 
of  the  thin  border  of  the  mantle,  and  only  when  irritated 
uses  the  ambulatory  pipe  for  darting  backwards.  The 
outer  skin  or  integument  of  the  disc  of  attachment  is  so 
thin  that  the  ink  bag  can  be  clearly  seen  near  the  center 
of  it.  .According  to  Bather,1  one  larval  Sepia,  when 
irritated,  ejected  ink  twice  within  one  minute  of  being 
taken  from  the  egg-capsule.  The  ink,  however,  was  not 
sufficiently  dense  to  obscure  the  motions  of  the  animal. 

The  adult  (No.  632  ;  No.  633,  model  of  the  same) 
loses  the  habit  of  attaching  itself  and  of  swimming  by  its 
mantle,  while  the  ambulatory  pipe  becomes  the  chief 
means  of  rapid  locomotion.  The  ink  bag  is  large  and 
an  efficient  means  of  protection.  The  pro-ostracum  or 
pen  is  developed,  being  the  calcareous  portion  familiarly 
known  as  cuttle  bone.  At  its  base  there  is  a  vestige  of 
the  chambered  shell,  while  the  guard  has  become  nearly 
obsolete.  These  animals  have  short,  stout,  bag-like 
bodies  with  eight  short  arms  and  two  longer  ones.  The 
alcoholic  specimen,  No.  632,  exhibits  the  open  mouth 
with  its  horny,  beak-like  teeth.  There  are  two  of  these 
and  the  lower  one  is  the  larger.  The  ambulatory  pipe 
is  conspicuous.  The  cuttlefish  possesses  an  ink  bag 
which  contains  the  sepia  used  as  the  basis  of  the  pig- 
ment. 

The  squid  is  another  living  representative  of  the  more 
specialized  Cephalopods,  which  has  lost  both  external 
and  internal  chambered  shell  and  has  nothing  but  a 
horny  pen.  This  pen  is  situated  in  the  dorsal  part  of 
the  mantle  and  can  be  of  little  use  to  the  animal.  The 
eggs  of  the  squid  are  in  long,  pod-like  cases  (No.  634), 
which  are  fastened  together  in  large  clusters.  In  its 
development,  and  in  that  of  all  Cephalopods,  definite 

Journ.  of  Malacology,  IV,  No.  2,  1895. 


260  SYNOPTIC    COLLECTION. 

traces  of  the  veliger  stage  (which  has  been  described  in 
the  Pelecypods  and  Gastropods)  are  entirely  lost  by  the 
law  of  acceleration  in  development. 

The  squid  (No.  635,  Loligo  vulgaris  Lam.),  has  a  long 
body  covered  with  a  leathery  mantle  with  a  fin  on  either 
side  of  the  posterior  end.  At  the  forward  end  the  mantle 
is  free,  so  that  the  water  passes  into  the  cavity  of  the 
body,  and  bathes  the  two  gills  which  are  placed  one  on 
either  side  (see  preparation,  No.  636).  After  the  water 
has  flowed  in,  the  mantle  is  applied  closely  to  the  neck  so 
that  the  body  cavity  is  a  tight  bag  with  only  one  opening, 
and  that  is  the  ambulatory  pipe  or  hyponome  which  we 
found  in  the  Nautilus.  The  forcible  ejection  of  the  water 
through  this  pipe  sends  the  animal  swiftly  backwards. 
The  waste  products  of  the  body  and  the  inky  fluid  for 
protection  are  also  discharged  through  this  pipe.  The 
head  of  the  squid  is  provided  with  two  eyes  which  are 
more  highly  organized  than  any  other  invertebrate  eye, 
but  have  only  a  superficial  resemblance  to  the  vertebrate 
eye.  The  mouth- has  a  horny  beak  and  a  lingual  ribbon. 
It  is  surrounded  by  eight  short  arms  and  two  long  ones 
which  have  suckers.  In  the  preparation  (No.  636)  an 
incision  has  been  made  along  the  middle  of  the  ventral 
side,  and  the  mantle  laid  back  exposing  the  internal 
organs.  A  slender  tube,  the  esophagus,  extends  from 
the  mouth  to  the  long,  sac-like  stomach  which  has  a  bag- 
like  coecum  near  the  pyloric  or  forward  end.  The  intes- 
tine, another  slender  tube,  is  seen  running  forward  from 
the  stomach  under  the  liver,  and  by  the  side  of  the  duct 
of  the  ink  bag.  The  anus  and  the  outlet  of  the  duct  are 
near  the  base  of  the  ambulatory  pipe  and  directly  in  the 
path  of  the  outgoing  current  of  water  which,  as  we  have 
already  said,  carries  away  the  products  of  both  intestine 
and  ink  bag.  The  heart  is  situated  near  the  base  of  the 
gills  ;  back  of  it  and  occupying  the  greater  part  of  the 
body  cavity  is  the  mass  of  eggs. 

The  embryo  of  Octopus  has  a  shell  sac  on  the  forward 


METAZOA  —  MOLLUSCA.  201 

part  of  the  dorsal  side  of  the  body,  but  as  it  develops 
this  shell  sac  becomes  aborted  and  neither  the  young 
(No.  637)  nor  the  adult  Octopus  (No.  638)  have  a 
vestige  of  a  shell.  The  animal  is  built  upon  the  same 
plan  of  structure  as  the  squid.  The  model  shows  the 
natural  position  of  the  Octopus  with  the  mouth  downward 
and  long  arms  extending  out  on  all  sides,  provided  with 
the  sucking  discs  that  make  this  animal  a  formidable 
one.  Above  is  the  great  rounded  head  with  its  prom- 
inent eyes. 

The  alcoholic  specimen  (No.  639)  shows  the  large  open 
hyponome,  the  arms  surrounding  the  mouth,  and  the 
round  plump  body.  The  membrane  that  connects  the 
base  of  the  long  tapering  arms  and  the  suckers  are  well 
seen  in  No.  640.  The  hyponome  in  this  specimen  is 
small. 

In  Elcdone  aldrovandi  Delle  Chiaje  (No.  641),  there  is 
but  one  row  of  suckers  on  the  arms.  Loligopsis  verani 
Fer.  (No.  642),  has  a  more  slender  body  and  two  very 
long  delicate  arms. 

Argonauta  argo  Linn.,  or  the  Paper  Nautilus  (No.  643, 
eggs,  2  females,  i  male)  is  related  to  the  Octopus,  the 
structure  of  the  two  animals  being  similar.  Here  we 
have  no  shell  comparable  with  that  of  other  Cephalopods. 
The  male  (No.  643,  alcoholic  specimen  ;  No.  644,  model) 
is  without  any  protective  covering,  but  the  female  (No. 
643,  alcoholic  specimen  ;  No.  645,  model)  has  an  egg 
case  (No.  646)  of  exquisite  beauty.  This  case  is  in  the 
form  of  a  spiral  shell,  and  is  developed  late  in  a  post- 
embryonic  stage.  It  is  composed  of  three  layers,  one 
made  by  the  edge  of  the  mantle,  another  by  the  whole 
mantle,  and  the  outer  layer  by  the  two  large  arms  (see 
No.  645).  The  last  named  layer  does  not  occur  in  the 
shells  of  other  Cephalopods. 

The  male  is  very  much  smaller  than  the  female.  One 
of  the  arms  becomes  modified  and  enclosed  in  a  sac,  as 
seen  in  No.  644.  Later  this  sac  splits  and  the  arm  is 


262  SYNOPTIC    COLLECTION. 

free  (No.  644).  The  two  halves  of  the  sac  then  reunite 
and  the  sac  thereby  formed  becomes  filled  with  spermato- 
zoa. The  arm  with  the  sperm  is  detached  and  finds  its 
way  to  the  mantle  cavity  of  the  female.  No.  645  shows 
the  two  large  arms  of  the  female  that  have  become  greatly 
modified  in  structure.  In  the  alcoholic  specimen  these 
are  much  contracted.  They  are  usually  applied  closely  to 
the  outer  surface  of  the  shell  and  are  not  carried  as  sails 
though  often  so  figured  in  the  books. 

The  Argonaut  propels  itself  through  the  water  in  pre- 
cisely the  same  way  as  the  squid,  having  the  same 
hydraulic  apparatus. 

The  Mollusca  constitute  a  subkingdom  of  immense  size 
and  unnumbered  variations.  Underlying  these  variations, 
however,  there  is  a  fundamental  unity.  Most  Mollusca 
pass  through  a  trochophore  and  a  veliger  stage  in  their 
development ;  most  possess  a  shell  gland  the  first  product 
of  which  is  a  simple,  unornamented,  colorless  or  slightly 
colored,  plate-like  shell.  If  this  plate-like  shell  divides 
into  two  parts  the  result  is  a  bivalve  shell,  the  distinctive 
character  of  the  class  of  Pelecypods.  If  it  becomes  a 
spiral  cone,  the  univalve  shell  and  the  class  of  Gastropods 
results.  If  the  spiral  cone  becomes  chambered,  the 
product  is  the  shell  peculiar  to  the  Cephalopods. 

Free-moving,  sedentary,  and  boring  habits  produce 
modifications  in  the  shell.  Among  Pelecypods  the  free- 
moving  species,  as  a  rule,  have  equivalved.  symmetrical 
shells,  while  the  sedentary  forms  are  unequivalved  and 
asymmetrical.  The  boring  habit  in  both  Pelecypods  and 
Gastropods  tends  towards  the  reduction  of  the  shell,  until 
only  a  vestige  of  it  remains.  Other  causes  have  produced 
a  similar  reduction.  The  free-swimming  habits  of  the 
Heteropods  have  resulted  in  the  development  of  a  fin-like 
organ,  while  the  shell,  being  of  little  use,  has  become 
small  and  inconspicuous.  The  Nudibranchs  carry  the 
process  still  farther,  since  they  possess  a  shell  in  the 


METAZOA MOLLUSCA.  263 

embryonic  stage  only,  which  is  quickly  lost,  so  that  the 
adult  is  without  even  a  vestige  of  a  protective  covering. 

The  marine  Gastropods  probably  gave  rise  to  the 
specialized  fresh-water  and  terrestrial  species,  transi- 
tional forms  existing  at  the  present  time. 

The  Cephalopoda  illustrate  acceleration  in  development 
and  specialization  in  structure.  The  external,  chambered 
shell  becomes  internal  and  extremely  modified ;  it  may 
also  exist  as  a  vestige  or  be  wanting  altogether. 


METAZOA VERMES.  265 


VERMES. 

Section  n  and  12  (in  part). 
BRACHIOPODA.  —  ATREMATA. 

The  class  of  Brachiopoda,  as  already  stated,  is  one  of 
the  best  for  illustrating  a  classification  based  on  the  -stages 
of  growth  and  decline. 

The  ancestral  form,  Paterina,  which  Beecher  described 
and  figured,1  is  now  considered  by  Walcott2  to  be  identi- 
cal with  the  genus  Iphidea ;  and  in  the  Iphidea,  Walcott 
has  found  a  rudimentary  cardinal  or  hinge  area.  This 
fact  prevents  the  Iphidea  and  the  Paterina,  if  they  be  the 
same,  from  representing  the  most  primitive  form  conceiva- 
ble; that  is,  a  shell  without  even  the  rudiment  of  a  cardi- 
nal area.  There  is  little  doubt,  however,  that  such  a 
primitive  form  existed  and  in  time  will  be  discovered. 
To  such  a  genus,  when  found,  the  name  of  Paterina 
should  surely  be  given  in  consideration  of  Beecher's 
classic  researches  on  the  class  of  Brachiopoda.  Until  this 
new,  theoretical  form  is  brought  to  light,  we  will  bear  in 
mind  that  the  Iphidea  is  the  simplest  form  yet  discovered 
and  described,  while  at  the  same  time  we  shall  accept  the 
shell  as  described  by  Beecher  under  the  name  of  Paterina 
as  representing  the  still  more  primitive  form  that  is  to  be 
discovered. 

This  Paterina  shell  is  simple  in  youth  (PI.  647,  fig.  i, 
P.  labradorica  Billings,  pedicle  valve)  and  also  in  maturity 
(fig.  2,  brachial  valve),  having  two  nearly  equal  valves 
which  are  semi-elliptical  in  shape.  The  hinge  line  is 
straight  and  nearly  equal  in  length  to  the  width  of  the 

1  Amer.  Journ.  Sci.,  (3),  XLI,  1891  ;  (3),  XLIV,  1892. 

2  Proc.  U.  S.  Nat.  Mus.,  XIX,  1897,  pp.  707-718. 


266  SYNOPTIC    COLLECTION. 

shell.  The  lines  of  growth  run  parallel  with  one  another 
and  there  is  no  ornamentation  of  any  kind.  The  new 
layers  of  shell  are  added  at  the  anterior1  and  lateral 
margins,  so  that  the  pedicle  at  the  posterior  end  is  always 
free. 

The  embryonic  shell  (uncolored  in  PL  647,  figs,  i,  2) 
or  protegulum  (meaning  early  covering)  is  similar  in  form 
to  the  mature  shell.  As  we  have  already  said,  the  youth- 
ful (nepionic),  adolescent  (neanic),  and  mature  (ephebic) 
stages  are  all  alike  (see  PI.  647,  figs.  i.  2),  so  that  it  is 
impossible  to  tell  where  one  stage  ends  or  another  begins. 

The  valves  of  the  shell  are  not  articulated  together  by 
teeth  and  sockets,  but  are  held  in  place  by  muscles.  The 
pedicle  valve  is  slightly  more  convex  than  the  brachial 
valve,  so  that  an  opening  is  produced  through  which 
passes  the  short  pedicle.  This  opening,  according  to 
Beecher's  figures,  is  shared  alike  by  both  valves,  so  that 
the  pedicle  is  free.  As  already  stated,  Walcott  has  found 
the  region  between  the  two  valves  more  or  less  closed  by 
rudimentary  cardinal  areas. 

Plate  648,  figs.  1-4,  represents  Walcott's  figures  of 
Iphidea.  The  brachial  valve  is  seen  in  fig.  i  ;  fig.  2  is 
a  summit  view  of  the  pedicle  valve  ;  while  a  side  view  of 
the  same  is  shown  in  fig.  3.  The  imperfectly  defined, 
rather  narrow  cardinal  area  is  shown  in  fig.  4  with  a  broad 
plate,  called  the  prodeltidium,  just  under  the  beak.  The 
latter  is  formed  by  the  pedicle  and  not  by  the  mantle  as 
is  the  case  with  the  deltaria  (see  p.  277). 

The  ancestral  species  from  the  Cambrian  and  Lower 
Silurian,  Obolella  polita  Hall  (No.  649  ;  PL  650,  fig.  i), 
had  a  more  or  less  circular  form.  This  shape  of  the  adult 
shell  is  peculiar  to  many  young  Brachiopoda,  so  that  when 

1  In  order  to  see  the  characteristic  parts  plainly,  the  specimens  are 
mounted,  and  the  figures  are  drawn,  with  the  anterior  end  towards 
the  observer.  This  is  contrary  to  the  usual  rule  which  places  the 
animal  with  the  forward  end  away  from  the  observer — the  most 
favorable  position  when  comparison  with  his  own  body  is  desired. 


METAZOA VERMES.  267 

they  attain  this  form  they  are  said  to  be  in  the  Obolella 
stage  of  development. 

Each  valve  of  Obolella  had  a  rudimentary  cardinal  or 
hinge  area  in  which  a  groove  was  scooped  out  for  the  pedi- 
cle. This  groove  is  seen  in  an  interior  view  of  the  bra- 
chial  valve  (fig.  2)  and  still  more  clearly  in  the  pedicle 
valve  (fig.  3).  The  markings  in  the  interior  of  the  valves 
(figs.  2,  3)  are  the  scars  left  by  the  muscles. 

One  of  the  more  progressive  species  closely  related  to 
Paterina  and  Obolella,  is  Trimerella  (PI.  651,  fig.  i,  T. 
ohioensis  Meek,  external  view  of  pedicle  valve  ;  fig.  2,  inter- 
nal view)  which  has  a  large  hinge  area,  finely  seen  in  fig. 
2,  and  a  furrow  bounded  by  ridges,  the  inner  edges  of 
which  serve  as  teeth.  This  primitive  mechanism  is  sug- 
gestive of  the  more  perfect  articulation  by  teeth  and 
sockets  of  the  more  specialized  Brachiopoda. 

Paterina,  Obolella,  and  Trimerella  represent  the  Atre- 
mata,  to  which  group  of  Brachiopoda  Lingulepis  (No.  652) 
and  Lingula  (No.  654)  also  belong.  In  Lingulepis  (No. 
652,  L.  pinniformis  Owen,  =  Lingula  antiqua  Hall)  the 
shape  is  rounded  and  similar  to  Obolella.  The  valves 
are  also  unequal,  and  in  other  structural  characters  this 
genus  is  intermediate  between  the  Obolellidae  and  the 
more  specialized  Lingulidae  represented  by  Lingula. 

The  power  of  resisting  adverse  conditions  is  so  great  in 
Lingula  that  it  has  come  down  to  us  essentially  unchanged 
in  structure  from  the  early  geologic  period  known  as  the 
Ordovician,  which  followed  the  Cambrian.  Its  persist- 
ence in  time,  according  to  Hall,1  is  "unequaled  by  that 
of  any  other  known  genus  of  organisms." 

The  embryonic  shell  of  the  Lingula  living  to-day  is 
similar  to  that  of  Paterina.  PI.  653,  figs.  1-3,  represents 
a  closely  allied  genus,  Glottidia  albida  Hinds.  Fig.  i 
shows  the  Paterina-like  shell  (left  unshaded  in  the  draw- 
ing) and  the  long  hinge  line  ;  also  the  youthful  (nepkmic) 

1  Pal.  N.  Y.,  VIII,  part  i,  1892,  p.  7. 


208  SYNOPTIC    COLLECTION. 

stage  when  the  shell  has  assumed  the  more  rounded  out- 
line of  Obolella.  That  this  stage  is  more  specialized  than 
the  Paterina-stage  ,is  proved  by  the  fact,  that,  whenever 
the  two  stages  occur  in  the  development  of  a  species,  the 
Obolella-stage  always  follows  the  Paterina-stage.  The 
hinge  line  grows  narrower  in  the  neanic  (fig.  2)  and  the 
ephebic  stage  (fig.  3),  while  the  shell  becomes  tongue- 
shaped  in  form. 

The  larva  of  the  living  Lingula  is  free  swimming,  but 
soon  a  pedicle  is  developed  which  becomes  a  long  flexible 
organ  in  the  adult  (No.  654).  This  pedicle  is  not 
attached,  but  the  end  is  buried  in  the  sand  and  protected 
by  a  tube  made  of  sand  grains,  after  the  fashion  of  the 
protective  coverings  of  worms.  According  to  Morse1  the 
Lingula  partially  recedes  into  its  sand  tube  after  the 
manner  of  worms.  The  shell  is  in  a  line  with  the  pedicle, 
and  the  length  and  flexibility  of  the  latter  organ  allow  the 
shell  freedom  of  motion  in  any  direction. 

Beecher'2  has  shown  that  physical  forces  acting  simi- 
larly on  all  sides  of  a  shell,  which  in  this  case  is  made 
possible  by  the  long  pedicle,  tend  to  produce  equal  valves, 
such  as  are  seen  in  Lingula. 

Comparative  simplicity  of  structure  marks  the  internal 
organs  as  well  as  the  external  characters  of  the  Atremata. 
The  fleshy  body  takes  up  the  greater  part  of  the  shell, 
while  the  arms  or  brachia  (the  characteristic  organs  which 
have  given  the  name  of  Brachiopoda  or  arm-footed  animals 
to  the  group)  are  without  limy  supports  of  any  kind. 
Since  these  organs  are  of  importance  in  determining  the 
phylogenetic  relations  of  genera,  we  will  give  figures  to 
illustrate  their  stages  of  development.  Their  mode  of 
growth  "is  alike  in  the  larval  stages  of  all  Brachiopods." 
They  first  develop  tentacles  in  pairs  on  each  side  of  the 
median  line  in  front  of  the  mouth.  This  stage  is  repre- 

1  Proc.  Boston  Soc.  Nat.  Hist.,  XV,  1873,  p.  372. 

2  Amer.  Journ.  Sci.,  (3),  XLI,  April,  1891. 


METAZOA  —  VERMES.  269 

sented  in  Glottidia  and  Lingula  in  PI.  655,  figs.  1-4.  New 
tentacles  are  continually  added  at  the  same  points,  until 
by  pushing  back  the  older  ones  a  complete  circle  is  formed 
about  the  mouth  (fig.  2),  which  later  becomes  introverted 
in  front  (fig.  3).  From  this  common  and  simple  struc- 
ture are  developed  all  the  complicated  brachia  of  the  more 
specialized  orders  (Beecher).  In  the  case  of  Lingula  the 
growing  points  at  which  new  tentacles  arise,  separate  and 
the  adult  possesses  two  coiled  arms  one  on  each  side  of 
the  median  line  (fig.  4). 

We  have  already  seen  that  members  of  the  Atremata, 
Trimerella  for  instance,  exhibit  specializations  of  struc- 
ture illustrating  progressive  tendencies,  but  the  group 
contains  no  old  age  forms. 

According  to  Beecher's  classification,  the  Atremata  are 
followed  by  the  Neotremata,  Protremata,  and  Telotre- 
mata,  the  first  two  being  the  more  primitive  orders  and 
the  last  two  the  more  specialized.  This  arrangement  is  in 
accordance  with  the  geological  history  of  the  four  orders, 
since  the  Atremata  were  the  first  to  appear  and  the  Telo- 
tremata  the  last. 

Schuchert's  classification1  gives  the  following  arrange- 
ment :  Atremata,  Telotremata,  Neotremata,  Protremata. 
This  investigator  makes  a  fundamental  division  of  the 
class  into  two  groups,  the  Homocaulia  or  those  Brachio- 
pods  in  which  the  pedicle  is  common  to  both  valves,  and 
the  Idiocaulia  in  which  the  pedicle  is  restricted  to  one 
valve.  The  Atremata  and  Telotremata  belong  to  the  first 
division,  according  to  Schuchert,  and  the  Neotremata  and 
Protremata  to  the  second. 

The  fact  that  the  Atremata  and  Neotremata  are  the 
most  primitive  of  the  four  orders  and  are  consecutive,  is 
not  considered  a  reason  by  Schuchert  for  placing  the  one 
after  the  other  in  a  classification.  Inasmuch  as  the  line 
of  descent  is  direct  from  Atremata  to  Telotremata  and 

1  Bull.  U.  S.  Geol.  Surv. ,  no.  87,  1897,  pp.  118-135. 


270  SYNOPTIC    COLLECTION. 

not  by  the  way  of  the  Neotremata  or  Protremata,  he  places 
the  Telotremata  next  the  Atremata. 

The  Neotremata  and  Protremata  branch  off  from  the 
Atremata  at  a  much  lower  geological  horizon  than  the 
Telotremata.  According  to  Beecher  the  Neotremata  have 
a  protegulum  like  that  of  the  Atremata  and  a  Paterina 
stage  when  the  pedicle  passes  out  freely  between  the 
valves.  According  to  Schuchert  the  pedicle  opening  in 
this  order  is  restricted  throughout  life  to  the  pedicle  valve. 
Even  if  this  be  true  with  the  forms  so  far  described,  we 
predict  that  other  forms  will  be  discovered  which  have 
the  pedicle  opening  common  to  both  valves  in  the  nepi- 
onic  stage. 

For  this  reason  we  shall  take  up  the  Neotremata  next, 
bearing  in  mind  that  more  investigations  are  needed  on 
the  fossil  forms  belonging  to  this  order,  as  well  as  on  the 
early  stages  of  development  of  existing  species. 

BRACHIOPODA. —  NEOTREMATA. 

One  of  the  more  primitive  members  of  the  Neotremata 
is  Paterula  (PI.  656,  figs,  i,  2.  P.  bohemica  Barr.).  It  has 
a  horny  shell  and  when  young  is  similar  to  Paterina,  but 
later,  layers  are  put  on  the  brachial  valve  (fig.  i)  posteriorly 
to  the  beak  which  cause  the  beak  to  become  internal  and 
the  shell  circular  in  outline.  The  pedicle  valve  (fig.  2)  is 
differentiated  from  the  brachial  by  having  a  notch  in  the 
margin  which  remains  open  in  the  adult  (fig.  2).  The 
arms  or  brachia  in  Paterula  are  two  single  spirals  without 
limy  supports. 

Another  genus,  Discinisca  (No.  657,  D.  laevis  Sow.),  has 
the  protegulum  of  the  brachial  valve  at  the  margin  in  the 
youngest  stage  and  later  near  the  margin,  but  with  growth 
the  protegulum  becomes  surrounded  by  more  layers,  as 
seen  in  No.  657.  The  edge  of  the  pedicle  valve  (No. 
657)  is  notched  on  the  margin  for  the  passage  of  the 


METAZOA VERMES.  271 

pedicle,  but  this  notch  becomes  surrounded  by  shell  lay- 
ers in  the  adult.  This  mode  of  growth  is  also  peculiar 
to  Discina,  another  member  of  the  Neotremata,  and  when 
it  occurs  in  the  more  specialized  groups  of  Brachiopods 
it  is  usually  called  the  Discinoid  stage  of  development. 

One  of  the  most  instructive  forms  is  Orbiculoidea  (No. 
658,  O.  lamellosa  Hall ;  No.  659,  O.  mimita  Hall;  PI.  660, 
figs.  1-4,  the  same  species;  No.  661,  O.  nitida  Phillips). 
Beginning  with  the  protegulum,  it  passes  through  the  Pa- 
terina  stage  (No.  659;  PI.  660,  fig.  i)  with  its  nearly 
equal  valves,  straight  external  or  marginal  hinge  line, 
and  its  concentric  parallel  growth  lines.  The  pedicle 
passes  out  freely  between  the  two  valves.  This  is  the 
early  nepionic  stage.  In  the  later  stage,  layers  of  shell 
have  encircled  the  protegulum  (No.  659  ;  PI.  660,  fig.  2)> 
causing  the  shell  to  become  circular  in  outline,  like  Obo- 
lella,  with  no  hinge  line,  and  with  the  beaks  internal 
though  still  near  the  margin. 

In  the  neanic  stage  the  beak  is  still  farther  from  the 
margin  (No.  659)  while  in  the  ephebic  stage  (No.  659) 
it  is  slightly  less  eccentric  and  would  seem  to  be  passing 
into  the  gerontic  stage.  The  condition  of  the  adult  bra- 
chial  valve  as  compared  with  that  of  the  young  is  shown 
in  PL  660,  fig.  4. 

The  pedicle  valve  (No.  658,  a,  b;  PI.  660,  fig.  3),  has 
the  protegulum  at  the  center  and  an  open  pedicle  notch 
as  in  the  adult  Paterula,  but  later  the  formation  of  circu- 
lar layers  of  shell  converts  this  notch  into  a  hole  through 
which  the  pedicle  passes  (No.  658,  a,  b).  This  hole  be- 
comes partly  filled  with  a  plate  called  the  listrium  (see 
No.  658,  a,  b). 

It  is  probable  that  Crania  (No.  662,  C.  anomala-,  No. 
663,  C.  tubinata  Poli)  represents  a  reduced  and  specialized 
condition  of  the  Neotremata.  The  complete  life  history 
of  this  genus  has  never  been  figured  and  described.  It 
is  known  that,  when  young,  the  pedicle  valve  has  an  open 
notch  like  that  of  the  adult  Paterula.  It  is  probable  that 


272  SYNOPTIC    COLLECTION. 

very  early  this  notch  is  surrounded  by  shell  layers, 
although  no  specimen  showing  this  holoperipheral  growth 
has  been  found.  This  is  probably  due  to  the  fact '  that 
when  very  young  the  animal  becomes  attached  to  a  rock 
(No.  663)  by  its  pedicle  valve  which  causes  the  pedicle 
to  disappear  and  with  it  the  notch  and  the  circular  layers 
if  any  such  exist. 

BRACHIOPODA. —  PROTREMATA. 

The  Protremata  may  have  arisen  from  some  Paterina- 
like  ancestor  which  lived  in  pre-Cambrian  times,  or  may 
have  branched  off  from  the  Neotremata  at  a  later  period. 
The  forms  known  to  us  illustrate  specialization  of  struc- 
ture brought  about  through  acceleration  in  development. 

One  of  the  more  generalized  forms  is  Kutorgina  cingu- 
lata  Billings  (PL  664,  figs.  1-3).  Here  the  hinge  line  is 
straight  (fig.  i),  and  there  is  a  narrow  rudimentary  cardinal 
area  on  the  pedicle  valve  (figs,  i,  2,/z').  This  valve  (fig. 
3)  rises  above  the  brachial  (figs.  1,2,  bv)  and  a  large  open- 
ing is  left  for  the  passage  of  the  pedicle  (fig.  2)  which  is 
only  slightly  restricted  by  the  deltidium.  This  plate  in 
the  Protremata  is  formed  in  the  embryo  and  is  a  shell 
growth  from  the  brachial  side  of  the  body  which  later 
becomes  attached  to  the  pedicle  valve.1  The  teeth  in 
Kutorgina  are  primitive  and  are  situated  at  the  outer  ends 
of  the  cardinal  area.  Figures  illustrating  the  stages  of 
development  are  given  under  Thecidium  (see  p.  273). 

The  brachial  valve  in  the  Protremata,  as  in  the  other 
orders,  is  less  differentiated  than  the  pedicle  valve,  and 
shows  the  protegulum  as  in  the  Atremata.  When  ex- 
tremely young,  the  shell  probably  passes  through  a  long- 
hinged  or  Paterina  stage,  but  in  the  early  nepionic  stage 
of  most  genera  the  pedicle  is  surrounded  by  shell  layers 

1  See  Beecher,  Amer.  Journ.  Sci.,  (3),  XLIV,  1892,  pp.  142-147. 


METAZOA VERMES.  273 

and  the  pedicle  valve  becomes  circular  in  form,  the  shell 
passing  through  a  stage  similar  to  that  which  we  have 
already  described  as  the  Discinoid  stage  of  the  Neotrem- 
ata.  This  is  shown  in  Leptaena  rhomboidalis  Wilck.  (PI. 
665,  fig.  i).  As  growth  continues,  the  neanic  stage  (fig. 
2)  is  marked  by  radiating  lines.  The  peripheral  layers 
are  resorbed,  so  that  the  pedicle  opening  approaches  the 
edge  (fig.  2)  and  in  the  ephebic  stage  reaches  it  (fig.  3; 
see  also  No.  666).  In  this  stage  the  cardinal  areas  of 
both  the  convex  pedicle  valve  (No.  666)  and  the  concave 
brachial  valve  are  long,  flat,  and  narrow  with  a  triangular 
fissure  for  the  pedicle  which  is  partly  filled  by  a  deltidium. 
Finally  the  pedicle  disappears  altogether,  and  Leptaena 
is  free  as  in  its  young  condition.  In  old  age  the  anterior 
and  lateral  portions  of  the  valves  bend  at  nearly  right 
angles  (No.  666)  to  the  plane  of  the  younger  shell,  and 
the  layers  of  growth  are  crowded  closely  together  (No. 
667). 

The  arms  or  brachia  in  Leptaena  and  in  the  Protremata 
generally  are  not  supported  by  a  limy  skeleton. 

The  only  living  representative  of  the  Protremata  is  the 
genus  Thecidium  (  =  Lacazella).  The  cephalula  stage 
(as  it  is  called)  is  represented  in  PI.  668,  fig.  i,  a  dorso- 
ventral  longitudinal  section  of  T.  mediterraneum  Risso. 
The  mantle  lobes  (fig.  i,  d  and  v)  are  unequal.  The 
limy  dorsal  valve  (ds)  and  the  shell-plate  (del)  begin  to 
form ;  the  latter  on  the  dorsal  side  of  the  body.  The 
larva  transforms  by  the  mantle  lobes  bending  upward, 
which  causes  the  shell-secreting  surfaces  (indicated  by  the 
heavy  black  lines)  to  come  on  the  exterior  (fig.  2).  The 
shell-plate  (del)  is  below  the  hinge  line  (fig.  2,  hi).  The 
adult  (fig.  3)  shows  one  valve  and  the  deltidium  (del), 
and  the  side  view  (fig.  4)  gives  both  valves  marked  by 
concentric  lines,  the  hinge  line  (hi)  and  the  deltidium 
(del). 

These  figures  show  that  the  deltidium  is  formed  on  the 
brachial  side  of  the  body,  as  already  stated,  and  on  that 


274  SYNOPTIC    COLLECTION. 

segment  which  subsequently  becomes  the  pedicle ;  after- 
wards it  is  fastened  to  the  pedicle  valve.  Thecidium  is 
especially  interesting  as  it  is  the  only  Brachiopod  which 
retains  a  true  deltidium  at  maturity.1 

It  is  instructive  to  note  that  after  the  pedicle  is  lost,  in 
several  genera  of  this  order,  spines  are  developed  for  the 
purpose  of  anchoring  the  animal.  In  Chonetes  granu- 
lifera  Owen  (No.-  669),  these  spines  are  found  only  on  the 
cardinal  margin  of  the  pedicle  valve.  Productus  nebras- 
kensis  Owen  (No.  670),  however,  inherits  such  a  weak 
pedicle  that  this  organ  soon  disappears,  and  spines  are 
developed  over  the  entire  surface  of  the  pedicle  valve  and 
sometimes  are  also  found  on  the  brachial  valve.  The 
animal  lies  on  the  pedicle  valve  fastened  by  its  spines. 

Vestiges  of  the  cardinal  areas  and  teeth  are  sometimes 
present  in  this  genus,  but  are  often  wanting.  The  beak 
is  high  and  curved,  and  no  trace  of  a  pedicle  opening 
remains.  Many  of  these  characters  are  intensified  in 
the  old  age  stage  (No.  671).  The  shell  extends  ante- 
riorly and  broadens  outward  at  the  same  time.  The 
beak  of  the  pedicle  valve  is  bent  far  inward  and  the  ped- 
icle opening  has  wholly  disappeared.  The  ribs  which 
are  prominent  and  regular  in  the  adult  stage,  partially 
die  out  and  become  more  or  less  irregular  (see  No.  671). 

Interesting  specializations  of  structure  are  illustrated 
by  Orthis  (=  Platystrophia 2)  (No.  672).  We  have  here 
large  cardinal  areas  and  perfect  articulation  by  teeth  and 
sockets.  The  area  of  the  pedicle  valve  has  a  large 
pedicle  opening  or  delthyrium,  and  that  of  the  brachial 
valve  has  a  similar  opening,  the  chelyrium.  When  young, 
these  openings  are  partially  closed  by  plates,  the  deltidium 
and  chilidium.  In  the  course  of  development,  however, 
the  plates  are  resorbed  so  that  open  passages  remain  in 
the  adult  (see  No.  672). 


1  Hail  and  Clark,  Nat.  Hist.  N.  Y.,   Pal.,  VIII,  part  2,  1894,  p. 
283. 

2  See  Cumings,  Amer.  Journ.  Sci.,  (4),  XV,  nos.  85,  86,  1903. 


METAZOA  —  VERMES.  275 

The  changes  which  take  place  in  the  development  of  a 
Protrematous  shell  are  well  shown  by  Bilobites  varicus 
Conrad  (PI.  673,  figs.  1-12).  It  begins  as  a  smooth, 
straight-hinged  form  with  the  hinge  as  broad  as  the  shell 
and  with  a  rounded  front  margin  (figs,  i,  2).  Occasion- 
ally while  the  shell  is  in  the  nepionic  stage  the  deltidium 
of  the  pedicle  valve  is  retained,  as  seen  in  fig.  3,  which 
also  shows  the  cardinal  area  and  pedicle  opening.  The 
deltidium  is  lost  in  the  neanic  or  the  ephebic  stage  and  the 
pedicle  passes  out  of  the  large  opening.  Gradually  the 
rounded  front  margin,  seen  in  figs.  1,2,  becomes  straight 
(fig.  4),  and  later  a  sinus  is  developed  (fig.  5)  which 
afterward  becomes  more  pronounced  (figs.  6-n). 

The  pedicle  valve  is  at  first  shorter  than  the  brachial, 
and  for  this  reason  is  not  seen  in  figs.  1,2,  4-6  ;  soon, 
however,  it  grows  longer  (fig.  7)  and  the  cardinal  area 
with  its  pedicle  opening  is  distinctly  seen  (figs.  8-10). 
The  adult  shell  (fig.  u)  has  a  narrow  hinge  line,  while 
the  anterior  portion  of  the  shell  is  broad  and  strongly 
bilobed.  In  the  old  age  or  gerontic  stage  the  sinus 
becomes  nearly  obliterated  (fig.  12).  and  the  anterior 
portion  of  the  shell  resembles  that  of  the  young  stage 
represented  in  fig.  5. 

One  of  the  most  differentiated  members  of  the  Protre- 
mata  is  the  genus  Pentamerus  (No.  674,  P.  oblongus 
Sow.).  The  variation  in  form  of  this  genus  is  shown  by 
the  specimens  (No.  674,  e,  f)  which  are  casts  of  the 
interior.  The  beaks  even  in  the  young  stages  (No.  673, 
a-d)  are  incurved,  and  so  strongly  is  this  the  case  in  the 
adult  (e,  f)  that  the  small  pedicle  opening  is  concealed. 
The  deltidium  when  present  (which  is  rarely  the  case)  is 
concave. 

This  genus  is  an  exception  among  the  Protremata,  inas- 
much as  the  arms  are  supported  by  two  limy  processes 
called  crura.  These  crura  unite  to  form  a  plate,  the  cru- 
rulium,  which  is  used  for  the  attachment  of  muscles. 
The  pedicle  valve  also  has  a  large,  strong,  internal  plate, 


276  SYNOPTIC    COLLECTION. 

the  "  shoe-lifter  "  or  spondylium,  which  serves   the  same 
purpose. 

BRACHIOPODA. —  TELOTREMATA. 

One  of  the  most  primitive  members  of  the  Telotremata 
is  Protorhyncha  aequiradiata  Hall  (PL  675,  figs.  1-3). 
We  know  nothing  of  the  early  development  of  this  spe- 
cies, but  the  adult  is  primitive  in  its  characteristics,  so 
that  it  is  reasonable  to  assume  that  the  young  stages 
must  have  been  still  more  primitive.  It  has  been  ascer- 
tained in  living  genera  of  this  order  (Telotremata)  that 
in  the  nepionic  and  early  neanic  stages  the  pedicle  passes 
out  freely  between  the  two  valves,  the  opening  being 
shared  by  both  as  in  the  Atremata.  In  the  later  neanic 
period  the  shell  layers  extend  entirely  round  the  pedicle, 
so  that  this  organ  becomes  restricted  to  the  pedicle  valve. 
In  the  adult  or  ephebic  stage  of  Protorhyncha  (figs.  1-3) 
the  pedicle  opening  is  triangular,  and  is  rarely  closed  by 
plates  of  any  kind. 

There  is  no  cardinal  area  in  Protorhyncha,  according 
to  Schuchert,1  while  Hall  and  Clarke2  figure  a  small  rudi- 
mentary area  (fig.  2).  The  adult  shell  is  narrow  at  the 
beak  or  rostrate  in  form  (PL  675,  fig.  i,  internal  cast  of 
the  brachial  valve;  fig.  3,  internal  cast  of  the  pedicle 
valve). 

The  arms  of  Protorhyncha  are  fleshy  and  not  strength- 
ened by  limy  supports ;  even  crura,  the  parts  to  which  the 
brachial  supports  are  fastened,  are  not  developed. 

According  to  Schuchert  3  the  oldest  Rhynchonelloids 
are  rostrate  in  form,  like  Protorhyncha,  and  the  ontogeny 
of  several  living  species  of  the  genus  has  not  revealed  a 
long-hinged  stage. 

1  Bull.  U.  S.  Geol.  Surv.,  no.  87,  1897,  p.  87. 

2  i3th  Ann.  Rep.  State  Geol.  N.  Y.,  1893. 

3  Loc.  cit.,  p.  83. 


METAZOA VERMES.  277 

Rhynchonella  peregrina  (No.  676)  from  the  Cretaceous, 
Rhynchonella  octoplicata  (No.  677),  and  Rhynchonella 
psittacea  Dvds.  (=  Ffemithyris  psittacea  Chemnitz)  (No. 
678  ;  No.  679,  shells  of  the  same),  living  to-day,  show 
no  marked  difference  in  form  from  the  primitive  Pro- 
torhyncha  of  the  Silurian  formation,  although  the  size 
varies,  Rhynchonella  peregrina  being  the  giant  of  the 
genus.  This  species  exhibits  the  curved  hinge  line  (No. 
676),  the  prominent  beak,  and  the  pedicle  opening  which 
is  partly  closed  by  two  plates  called  by  Hall  and  Clarke 
deltaria.  The  origin  of  these  plates  is  entirely  different 
from  that  of  the  single  plate,  the  deltidium.  As  we  have 
already  seen  in  the  Protremata  (see  p.  272),  the  deltidium 
is  a  primitive  character  arising  in  the  embryo  or  early 
nepionic  stage  of  development,  while  the  deltaria  are 
formed  in  the  neanic  or  the  ephebic  stage  and  are  made 
by  extensions  of  the  mantle.  Owing  to  this  difference  in 
origin  and  structure,  and  in  order  to  save  confusion,  we 
prefer  the  name  of  deltaria  to  deltidial  plates  given  by 
many  naturalists. 

The  smooth,  unornamented  condition  of  the  young 
Rhynchonella  shell  is  seen  in  No.  677,  while  the  later 
stages  are  marked  by  ribs  and  flirtings.  Along  the  mar- 
gin, the  layers  are  crowded  closely  together,  an  indication 
of  the  gerontic  stage. 

The  specimen  of  Rhynchonella  psittacea  Dvds.  (No. 
678)  is  attached  to  a  pebble.  Unlike  Protorhyncha,  this 
genus  has  the  arms  supported  by  two  short,  simply 
curved  processes,  the  crura  (see  No.  679,  f;  PI.  680), 
which  are  attached  to  the  brachial  valve  (see  No.  678 
specimen  with  arms  extended). 

Specialization  of  parts  is  finely  illustrated  in  this  order 
by  the  structure  of  the  brachia  and  their  internal  limy 
supports  or  brachidia.  Beginning  with  the  simple,  curved 
crura  of  the  Rhynchonellae  (PL  680,  crura  with  the  fleshy 
arms  coiled),  we  pass  to  Centronella  (C.  glansfagea  Bill- 
ings; PI.  681,  fig.  i,  dorsal  view;  fig.  2,  ventral  view; 


278  SYNOPTIC    COLLECTION. 

fig.  3,  side  view),  in  which  a  primitive  loop  (fig.  4;  fig.  5, 
side  view  of  same)  descends  from  the  brachial  valve. 
This  is  made  by  two  leaf-like  parts  or  lamellae  which  are 
attached  to  the  crura  and  which  unite  in  the  median  line 
to  form  the  broad  loop. 

The  hinge  area  with  its  ridges  and  the  muscular  scars 
are  seen  in  fig.  6. 

Stringocephalns  burtini  Defr.  (PL  682  ;  No.  683)  is  a 
Devonian  representative  of  a  more  specialized  family. 
In  the  young  shell  (PI.  682,  fig.  i)  the  triangular  pedicle 
passage  or  delthyrium  is  open  or  sometimes  partly  closed 
by  partially  developed  deltaria  ;  in  the  adult  (PL  682,  figs. 
2-4  ;  No.  683)  it  is  wholly  closed  excepting  the  pedicle 
opening  (fig.  2),  while  in  the  old  age  stage  (fig.  5  ;  No. 
683,  specimen  on  the  right)  the  coalescence  of  the  plates 
into  one  plate  (called  the  deltarium  and  the  pseudodel- 
tidium)  is  almost  complete,  and  the  pedicle  opening  is 
greatly  reduced  in  size. 

The  arm  supports  consist  of  a  long  loop  which  extends 
around  the  margin  of  the  brachial  valve.  Its  form  and 
the  radial  filaments  extending  from  it  are  seen  on  the  left 
of  PL  682,  fig.  3.  The  strong  cardinal  process  extending 
from  the  brachial  valve  towards  the  large  median  septum 
of  the  pedicle  valve  on  the  right  is  also  well  seen  in  fig.  3. 

The  changes  which  a  Centronella-like  loop  often  under- 
goes are  well  illustrated  in  the  Palaeozoic  Brachiopod, 
Dielasma  turgidum  (PL  684,  figs.  1-5).  Fig.  i  is  the 
Centronella-like  loop  of  the  young.  The  pointed  ante- 
rior portion  is  resorbed  and  two  points  extend  forward 
(fig.  2).  The  process  of  resorption  continues  till  the 
loop  has  the  form  of  fig.  3.  In  the  loop  of  the  adult  the 
two  branches  or  lamellae  diverge,  as  seen  in  fig.  4,  x  6; 
fig.  5  is  a  side  view  showing  the  crus  and  loop  on  the 
right  and  the  median  septum  on  the  left. 

Among  the  instructive  forms  of  the  Telotremata  living 
to-day  are  Terebratula  and  Terebratulina. 

One  of  the  forms  of  Terebratula  (T.  insignis  d'Orb.; 


METAZOA VERMES.  279 

No.  685)  belonging  to  the  Jurassic,  was  of  remarkably 
large  size.  The  pedicle  opening  and  the  deltaria  are 
well  shown  in  the  specimen.  The  anterior  margin  exhibits 
the  gerontic  character  of  layers  crowded  closely  together. 

The  position  of  a  living  Terebratula  is  well  shown  in 
No.  686,  T.  vitrea  Born.;  also  No.  687,  where  the  Brachi- 
opod  is  attached  to  coral.  The  pedicle  is  tiny  for  the 
size  of  the  valves,  which  are  nearly  erect.  The  brachial 
valve  (No.  688,  b)  has  the  loop  attached  to  it.  This  loop 
began  as  a  primitive  Centronella  loop  and  passed  through 
changes  similar  to  those  which  will  be  described  farther  on 
in  the  closely  related  genus  Terebratulina.  The  pedicle 
valve  (No.  688,  c)  has  a  circular  pedicle  opening ;  the  del- 
taria are  small  and  concave,  so  that  the  brachial  valve 
moves  upon  the  pedicle,  though  the  motion  is  limited, 
especially  in  the  older,  more  rotund  specimens. 

The  development  of  Terebratulina  septentrionalis  Couth. 
(PI.  689,  figs.  1-7;  No.  690),  throws  light  on  several 
important  points.  The  earliest  stage  observed  after  the 
egg-stage  is  represented  in  fig.  i,  where  the  animal  is 
extremely  minute,  the  length  of  its  shell  being  indicated 
by  the  line  enclosed  in  the  circle.  It  is  attached  to  a 
rock,  and  rests  upon  its  broad  hinge  area  with  the  anterior 
margin  uppermost,  as  seen  in  the  drawing.  The  shell  is 
comparatively  broad  and  short,  and  there  is  a  wide  pedi- 
cle opening.  Its  form,  however,  changes  rapidly,  becom- 
ing like  Lingula  (fig.  2),  though  still  retaining  the  wide 
anterior  margin. 

The  pedicle  is  long,  allowing  freedom  of  motion  to  the 
valves  which  are  seen  in  fig.  3  in  a  partial  lateral  view. 
The  animal  is  able  to  "  whirl  quickly  "  on  its  pivot-like 
pedicle,  and  is  represented  in  motion  and  at  rest  in  fig.  4, 
When  in  motion,  it  is  nearly  erect  with  the  valves  open, 
and  the  cilia  of  the  tentacles  are  active  in  catching  food  ; 
while  at  rest,  the  valves  are  closed  and  the  brachial  valve 
often  lies  on  the  rock  or  other  object  of  support.  Further 
development  causes  the  shell  to  broaden  out  anteriorly 
and  to  become  ornamented  by  ribs  (fig.  6). 


280  SYNOPTIC    COLLECTION. 

A  distinct  line  is  seen  in  this  figure  marking  off  the 
nepionic,  Lingula-like  stage  from  the  succeeding  neanic 
stage.  When  the  brachial  valve  is  thrown  open  (fig.  5), 
the  crura  (cr),  which  have  already  begun  to  form,  are  seen 
supporting  the  crown  of  tentacles.  The  changes  which 
take  place  in  the  external  shell  between  the  stage  repre- 
sented in  figs.  5,  6,  and  the  completed  shell,  fig.  7,  were 
not  figured  by  Morse.  The  development  of  the  cardinal 
region  of  the  pedicle  valve,  however,  was  given  (PL  691, 
figs.  1-4).  The  pedicle  opening  becomes  more  circular 
in  outline  and  truncates  the  beak  of  the  pedicle  valve 
(compare  figs.  1-4  in  PI.  691  ;  see  also  No.  692,  T.  crassei 
Dvds.).  The  deltaria  are  small  and  concave,  while  the 
teeth,  which  are  prominent  in  the  earlier  stages  (PI.  691, 
figs.  1-3,  t),  are  reduced  in  size  in  the  adult  (fig.  4,  /). 
The  development  of  the  brachial  loop  is  shown  in  PI.  691, 
figs.  5-8.  Beginning  as  little  swellings  or  processes  (fig. 
5,  <r),  the  crura  grow  larger  (fig.  6,  c),  reminding  one 
of  these  parts  in  Rhynchonella  (see  PI.  680;  No.  678). 
Then  the  loop  begins  to  form  (PI.  691,  fig.  7),  which  is 
completed  in  the  adult  (fig.  8). 

The  development  of  the  brachia  in  Terebratulina  illus- 
trates the  development  of  these  organs  in  the  Telotremata 
generally.  The  first  three  stages  are  similar  to  those  of 
Glottidia  in  the  Atremata  (see  PI.  655,  figs.  1-3).  The 
lophophore  in  the  first  stage  is  a  simple  crescent  with  few 
tentacles  (PI.  693,  fig.  i);  in  the  second  stage  the  tenta- 
cles have  increased  on  either  side  of  the  median  line  in 
front  of  the  mouth  and  have  been  pushed  backward  until  a 
complete  ring  has  formed  around  the  mouth  (fig.  2). 
Next,  the  anterior  edge  of  this  ring  bends  inward  (fig.  3). 
The  development  is  carried  still  further  in  Terebratulina 
by  the  formation  of  a  median  unpaired  arm  (fig.  4).  Fig. 
5,  T.  cancellata  shows  a  well  developed  spiral  arm  between 
the  two  lateral  arms. 

Certain  gerontic  peculiarities  are  seen  in  Terebratulina 
cancellata  Koch  (No.  694).  The  nepionic  shells  seen  in 


METAZOA  —  VERMES.  281 

.the  little  box  are  somewhat  flattened  and  the  beak  of  the 
pedicle  valve  is  in  a  nearly  normal  condition.  The  pedicle 
opening  is  large,  and  the  delthyrium  is  not  filled  with  the 
deltaria.  The  older  shells  on  the  standard  are  thickened 
and  have  a  sharp  anterior  edge.  The  pedicle  has  worn 
away  a  portion  of  the  beak,  while  the  deltaria  have  formed, 
and  the  suture  indicating  their  line  of  contact  can  be 
plainly  seen  in  the  specimen  in  the  lower  right  hand 
corner.  In  old  age  the  shell  becomes  so  rotund  that  the 
valves  when  separated  are  bowl-like  in  shape  (see  side 
view  of  the  shell  in  the  upper  right  hand  corner).  Each 
valve  is  thickened  along  the  margin  by  many  layers 
crowded  closely  together.  The  suture  of  the  deltaria 
has  disappeared,  leaving  apparently  a  single  plate,  the 
deltarium  or  pseudodeltidium.  The  brachial  loop  or  ring 
is  essentially  the  same  in  the  youngest  and  oldest  stages. 

It  now  seems  probable  that  Tropidoleptus  carinatus 
Conr.  (PI.  695  ;  No.  696)  is  an  ancestral  form  of  the 
family  Terebratellidae.  It  is  a  thin  shell  with  convex 
pedicle  and  concave  brachial  valve.  The  cardinal  area 
is  straight  and  narrow,  and  in  the  young  (PI.  695,  fig.  i) 
longer  than  the  greatest  diameter  of  the  shell,  but  in  the 
adult  (No.  696;  PI.  695,  figs.  2-4)  it  is  shorter.  The 
pedicle  passage  is  never  closed  by  a  deltidium  (fig.  4  ; 
fig.  5,  side  view  of  cardinal  area  enlarged),  but  a  chili- 
dium  is  well  developed  on  the  brachial  valve  (fig.  5). 
The  loop  (fig.  6)  consists  of  two  descending  branches  or 
lamellae  united  to  the  median  septum.  These  parts  are 
still  better  seen  in  fig.  7,  which  is  a  side  view  of  the  sep- 
tum loop  and  the  two  jugal  processes  extending  from  the 
lamellae. 

Cistella  neapolitana  Scacchi,  belonging  to  the  generalized 
Terebratellidae,  is  living  to-day.  Its  development  tends 
to  prove  that  Brachiopods  are  closely  related  to  Worms. 
No.  697,  with  models  1-10,  and  pi.  698,  figs,  i-io,  illus- 
trate the  development  of  this  genus.  The  egg  (No.  697, 
i)  is  unsegmented.  Its  division  into  two  spheres  is  seen 


SYNOPTIC    COLLECTION. 

in  (2).  These  two  stages  represent  the  protembryo. 
The  blastula  or  mesembryo  is  seen  in  (3) ,  where  there 
are  many  cells  around  a  central  cavity.  The  gastrula  or 
metembryo  (4)  is  formed  in  this  genus  by  the  turning  in- 
ward of  a  portion  of  the  outer  layer,  a  process  known  as 
embolic  invagination.  In  the  first  stage  of  the  neoembryo 
(5  ;  also  PI.  698,  fig.  i)  the  embryo  consists  of  two  seg- 
ments, the  cephalic  and  the  caudal.  Then  the  thoracic 
segment  develops  (No.  697,  6  ;  PI.  698,  fig.  2)  with  the  eye 
spots  and  the  four  bunches  of  setae.  A  side  view  of  this 
cephalula  stage  is  given  in  PI.  698,  fig.  3,  and  a  dorso- 
ventral  longitudinal  view  of  the  same  stage  in  fig.  4. 
The  mantle  lobes  now  cover  most  of  the  caudal  segment, 
and  the  cephalic  segment  is  shaped  like  an  umbrella  (No. 
697,  7).  This  is  the  completed  neoembryo.  The  mantle 
lobes  fold  upward  over  most  of  the  head  segment,  and  the 
larva  is  transformed  into  the  typembryo  (see  No.  6975.8  ; 
PI.  698,  fig.  5  ;  fig.  6,  longitudinal  section  of  the  same ; 
No.  697,  9,  the  completed  typembryo  showing  embryonic 
shell).  The  mantle  lobes  are  now  directed  forward  in- 
stead of  backward,  as  in  fig.  4,  and  the  shell-secreting 
surfaces  (indicated  by  the  heavy  black  line)  are  on  the 
outside  instead  of  the  inside.  This  stage  develops  into 
the  phylembryo  (No.  697,  10;  PI.  698,  fig.  7);  the  latter 
figure  shows  the  protegulum,  the  beginning  of  the  tenta- 
cles on  the  band  or  lophophore  (/),  the  hinge  line,  and 
the  teeth  (/)  at  the  outer  ends.  The  nepionic  stage  is 
represented  in  PI.  698,  figs.  8-10.  The  tentacles  are 
now  distinct  (fig.  8),  and  also  the  mouth,  stomach,  and 
muscles  are  shown  with  the  shell  and  the  pedicle.  The 
large  opening  between  the  valves  (filled  by  the  pedicle, 
/)  is  well  seen  in  figs.  9,  10,  which  are  a  dorsal  and  a 
side  view  of  the  nepionic  shell. 

The  family  Terebratellidae  is  especially  instructive  as 
it  offers  interesting  correlations.  Beecher  has  brought 
out  (see  PI.  699)  the  parallelism  existing  between  adult, 
permanent  generic  structures  of  the  more  primitive  mem- 


METAZOA VERMES.  283 

bers  of  this  family,  and  the  stages  in  the  ontogeny  of  the 
brachial  supports  of  the  specialized  members  ;  such,  for 
instance,  as  Magellania.  In  Gwynia  capsula  Jeffreys 
(PI.  699,  A),  one  of  the  most  primitive  members  of  the 
Terebratellidae,  the  brachial  supports  never  undergo  a 
metamorphosis  but  remain  essentially  the  same  through- 
out life.  They  consist  of  two  descending  branches  or 
lamellae  which  are  not  attached  to  the  crura  and  which 
do  not  unite  to  form  a  complete  loop.  The  crura  from 
which  the  lamellae  ultimately  extend  in  most  genera  are 
seen  at  the  posterior  end  of  the  valve  in  all  the  figures. 

Cistella  neapolitana  Scacchi  (PL  699,  B),  has  a  median 
septum  with  a  calcified  loop  attached  which  is  united  to 
the  crura. 

A  small  ring  appears  on  the  septum  in  Bouchardia  rosea 
Ma  we  (PI.  699,  C,  Ca,  side  view),  which  is  the  begin- 
ning of  the  secondary  loop.  The  parts  become  more 
united  in  Megerliiia  lamarckiana  Davidson  (D),  while  in 
Magas  pumilus  Sow.  (E),  the  descending  branches  are 
completed,  though  the  ascending  have  not  united.  Maga- 
sella  cumingi  Dvds.  (F),  shows  the  character  of  the  de- 
scending and  ascending  loop  more  distinctly,  which 
reaches  a  still  more  specialized  condition  in  Terebratella 
rubicunda  (G).  Here  we  have  the  descending  loop  with 
the  septum  and  connecting  band  or  jugum  and  the  com- 
pleted ascending  loop. 

A  further  change  takes  place  in  Magellania  flavescens 
Lam.  (PI.  699,  H),  in  which  the  septum  and  connecting 
bands  seen  in  Terebratella  have  been  resorbed.  These 
eight  figures  represent  as  many  adults  of  eight  different 
genera,  ranging  from  the  most  primitive  to  the  most  spe- 
cialized of  the  Terebratellidae. 

When  the  life  history  of  the  last  named  genus,  Magel- 
lania, is  studied,  it  is  found  that  it  epitomizes  in  its  own 
development  the  history  of  these  genera,  and  in  this  way 
the  history  of  the  family  to  which  it  belongs. 

The  larval  Magellania  is  without  calcified  brachial  sup- 


284  SYNOPTIC    COLLECTION. 

ports,  but  has  a  band  or  circlet  of  tentacles.  This  is  the 
larval  stage  corresponding  to  the  adult  primitive  Gwynia, 
and  is  therefore  called  the  Gwyniform  stage  (PI.  699,  Ai). 
Next  the  median  septum  appears,  which  is  the  Cistelliform 
stage  (Bi).  The  only  advance  over  this  condition  shown 
by  the  adult  Cistella  (PL  699,  B)  is  the  calcification  of 
the  band  which  bears  the  tentacles,  and  its  attachment  to 
the  crura.1  The  third  stage  shows  a  ring  on  the  septum 
(Ci,  Cai,  side  view  of  same)  which  is  the  Bouchardiform 
stage.  A  still  more  advanced  condition  is  seen  in  the 
Megerliniform  stage  (Di,  Dai,  side  view)  which  has 
the  septum  ring  and  in  addition  to  these  the  "  prongs  " 
of  the  descending  branches.  It  has  been  shown  '2  that 
in  "  all  genera  where  the  median  septum  is  highly  devel- 
oped the  calcification  of  the  lamellae  of  the  brachidium 
begins  quite  as  soon  from  the  lateral  wall  of  the  septum 
as  from  the  crural  bases  on  the  hinge-plate.  Calcification 
thus  proceeds  both  posteriorly  and  anteriorly." 

The  Magasiform  stage  exhibits  the  completion  of  the 
descending  branches  (Ei).  This  stage  and  also  the  Mag- 
aselliform  stage  (Fi)  which  follows,  show  the  union  of  the 
ascending  branches,  and  in  this  particular  differ  from  the 
adult  Magas  (E)  and  Magasella  (F). 

The  Terebratelliform  stage  (Gi)  is  similar  to  the  adult 
of  Terebratella  (G).  At  last  the  final  stage  is  reached, 
as  we  have  already  stated,  by  the  resorption  of  the  con- 
necting band  and  the  septum  (Hi,  Magellania  venosa 
Sol.). 

The  family  of  Atrypidae  is  represented  by  Zygospira 
and  Atrypa.  Zygospira  is  the  most  primitive  spire- 
bearing  genus  known.  Figs,  i-n  of  PI.  700  represent 
Zygospira  recurvirostra,  Z.  modes ta,  Z.  headi,  and  No. 
701  is  a  small  colony  of  Zygospira  modesta  Hall,  in 
which  the  shells  are  preserved  in  natural  position. 

1  Beecher,  Trans.  Conn.  Acad.  Sci.,  IX,  part  2,  1895,  p.  393. 

2  Hall  and  Clarke,  Nat.  Hist.  N.  Y.  Pal.,  VIII,  part  2,  1894,  p. 
305- 


METAZOA VERMES.  285 

The  brachial  support  in  the  young  Zygospira  is  a  Cen- 
tronelliform  loop  (PI.  700,  fig.  i  ;  fig.  2,  side  view  of  the 
same).  With  the  growth  of  the  shell  the  descending 
branches  of  the  loop  diverge,  while  the  resorption  of 
the  central  portion  of  the  loop  causes  the  formation  of 
the  cross  band  or  jugum,  as  seen  in  figs.  3,  4.  Both 
the  loop  and  the  jugum  become  more  slender  (Fig.  5), 
while  the  projections  on  the  descending  branches  of  the 
loop  are  the  beginnings  of  the  spiral  cones.  These  pro- 
jections grow  longer  (fig.  6)  and  begin  to  coil.  Fig.  7 
represents  a  young  individual  in  which  there  are  one 
and  a  half  turns  to  each  spiral.  In  the  mature  form 
(fig.  8)  there  are  about  three  volutions  in  each  spiral. 
The  adult  Zygospira  modesta  Hall  (figs.  9,  10)  has  five 
volutions,  while  the  species  Z.  headi  Billings  (fig.  n), 
has  six  whorls. 

At  the  same  time  that  the  whorls  have  increased  in 
number,  the  jugum  has  moved  posteriorly  (figs.  9-11), 
until  in  Z.  headi  it  is  seen  to  be  posterior  to  the  brachia 
(fig.  n).  The  spiral  arms  and  the  jugum  are  both  seen 
in  the  two  microscopic  preparations  (No.  702)  of  the 
shell  of  Zygospira. 

The  largest  number  of  whorls  of  any  member  of  the 
family  Atrypidae  is  reached  in  the  genus  Atrypa.  In 
A.  reticularis  Linn.,  from  the  Silurian,  sixteen  volutions 
have  been  counted  in  each  cone,  while  in  Devonian 
specimens  (Nos.  703,  704 ;  PI.  705)  twenty-four  volu- 
tions have  been  found.  These  are  directed  towards  the 
median  dorsal  region  and  fill  the  brachial  cavity.  The 
cross  band  or  jugum  is  continuous  in  the  young  but 
becomes  disunited  in  mature  specimens.  No.  704  shows 
the  club-shaped  ends  of  the  jugum  posterior  to  the  apices 
of  the  whorls  (see  PI.  705). 

One  of  the  most  specialized  families  of  the  Telotremata 
is  the  Spiriferidae,  represented  by  Spirifer  (No.  706,  S. 
grannlosus  Conrad;  No.  707,  S.  mucronatus  Conrad). 
Here  we  have  a  broad  shell  with  well  developed  cardinal 


286  SYNOPTIC    COLLECTION. 

areas  and  straight  hinge  line.  The  deltaria  are  formed 
and  become  united  into  one  plate,  but  with  age  they  are 
removed  by  accident  or  resorbed,  so  that  usually  the 
delthyrium  is  -open.1  In  the  old  age  stage  some  species 
form  a  callosity  in  the  pedicle  cavity  which  extends  across 
the  delthyrium  and  reaches  in  extreme  cases  nearly  to  the 
cardinal  margin.  The  median  septum  in  the  pedicle  valve 
is  found  in  the  young  but  seldom  in  the  adult. 

The  very  young  stages  of  some  species  of  Spirifer  have 
a  Centronella-like  loop  which  passes  through  a  metamor- 
phosis. The  descending  branches  in  this  genus  are  be- 
tween the  spiral  cones  (Nos.  706,  707),  and  the  apices  of 
the  latter  point  outward  and  upward  (No.  707).  The 
spiral  cones  (No.  706,  lower  left  hand  corner,  two  single 
specimens  from  two  shells)  may  have  a  greater  number 
of  volutions  in  the  adult  or  the  old  age  stage  than  any 
other  genus,  as  many  as  thirty-five  having  been  counted. 

The  jugum  is  discontinuous  and  is  represented  by  two 
short  processes,  one  of  which  is  seen  in  the  right  hand 
lamella  of  No.  707.  A  faint  median  septum  is  sometimes 
present  in  the  brachial  valve. 

Meristina  is  another  specialized  form.  No.  708,  M. 
maria  Hall,  is  a  vertical  section  through  the  outer  shell 
revealing  one  spiral  cone  and  cut  to  show  the  position  of 
the  loop.  In  No.  709  these  cones  are  seen  to  point  out- 
ward on  each  side  and  to  consist  of  many  whorls. 

Enough  has  been  said  to  show  that  there  is  a  far 
greater  degree  of  specialization  among  the  Telotremata 
than  in  the  other  three  orders  of  Brachiopods.  The  arm 
supports  are  extremely  complex,  and  the  devices  which 
have  arisen  to  meet  the  needs  of  the  muscular  system  are 
novel  and  various.  Unlike  the  Atremata  there  are  num- 
erous examples  of  old  age  forms  in  this  order. 

1  I3th  Ann.  Rep.  State  Geol.  N.  Y.,  1893,  II,  p.  752. 


METAZOA  —  VERMES.  287 

POLYZOA. 

The  young  stages  of  Polyzoa,  also  called  Bryozoa,  are 
similar  to  those  of  Brachiopods,  which  is  one  good  reason 
for  placing  these  two  groups  near  each  other.  The  Poly- 
zoa develop  from  a  trochophore  and  with  one  exception 
become  colonial  forms.  Their  calcareous  skeletons,  con- 
sisting of  numberless  little  cavities  or  chambers,  are  often 
seen  encrusting  seaweed.  Other  genera  are  like  minia- 
ture trees,  branching  coral,  and  the  like. 

Loxosoma  is  the  only  single  Polyzoan  known,  but 
inasmuch  as  it  is  a  commensal  living  with  other  animals, 
the  strong  probability  is  that,  though  single,  it  is  a  spe- 
cialized form,  a  reduced  descendant  of  some  colonial 
ancestral  species.  For  this  reason  we  consider  Pedicel- 
lina  (No.  710,  P.  cernua  Pall.)  as  the  more  primitive. 
Here  we  have  a  comparatively  simple  colony.  No.  710, 
a-h,  represents  eight  members ;  (a)  and  (b)  are  very 
young  stages  ;  (c)  is  also  young  with  its  tentacles  drawn 
in  ;  (d)  is  a  vertical  section  showing  mouth  (#z),  stomach 
(.$•),  and  anus  (an)  ;  (e)  and  (f)  have  the  tentacles  ex- 
panded ;  (g)  is  just  losing  its  old  cup-like  body  wall  or 
calyx  and  another  bud  is  beginning  to  grow  ;  in  (h)  the 
primary  calyx  has  been  lost  and  a  new  one  is  developing. 

It  is  seen  that  the  alimentary  canal  is  complete,  and 
that  it  makes  a  turn,  bringing  the  anus  near  the  mouth 
within  the  circle  of  tentacles.  This  position  of  the  anus 
is  characteristic  of  the  generalized  Polyzoa,  since  it  is 
found  outside  the  circle  of  tentacles  in  the  specialized 
forms. 

When  the  colony  of  Pedicellina  dies  there  are  left 
little  stalks  that  rise  from  a  creeping  stolon,  but  in  the 
specialized  Polyzoa  an  innumerable  number  of  tiny  cavi- 
ties or  zooecia  remain,  each  one  of  which  represents  an 
animal. 

Many   Polyzoa   are  of  exquisite  beauty,  as  shown  in 


288  SYNOPTIC    COLLECTION. 

some  of  the  species  (Nos.  711-721).  These  illustrate 
different  modes  of  growth  in  colonial  forms.  Cellularia 
(No.  711,  C.  rigida)  is  an  erect  species  with  its  many 
branches  made  up  of  joints.  The  beautiful  Catenicella 
(No.  712)  has  delicate  curling  branches,  while  Bugula 
(No.  713)  is  tree-like  in  form  and  some  species  show  a 
spiral  mode  of  growth.  Peculiar  modifications  of  struc- 
ture are  found  in  these  specialized  Polyzoa,  such  as  the 
birds'  heads  or  avicularia,  which  are  remarkable  organs 
of  uncertain  function.1  The  avicularia  are  well  illustrated 
by  Bugula  when  seen  under  the  microscope  (PI.  714). 
One  avicularium  (b)  is  seen  with  jaws  closed,  and  another 
(b')  with  the  lower  jaw  open.  These  little  organs  have 
been  seen  to  catch  small  animals. 

Biflustra  perfragilis  (No.  715)  is  an  extremely  fragile 
specimen  growing  in  a  circular  form.  In  Tessaradoma 
(No.  716,  T.  magnirostris)  there  is  one  layer  of  zooecia, 
while  in  Adeona  (No.  717,  A.  grisea)  the  zooecia  are  in 
two  layers.  In  general  form  Adeona  resembles  the  fan 
coral,  Rhipidogorgia.  The  colony  is  attached  by  a 
slightly  flexible  stem,  but  in  Adeonellopsis  (No.  718,  A. 
australis)  there  is  a  rigid  base. 

'Lepralia  (No.  719)  forms  a  large  colony,  and  the  flat- 
tened branches  unite  irregularly.  In  Filogrina  (No. 

720,  F.  implexd]    the  branches    appear   to    be    made    of 
strands. 

Among  the   fresh-water    Polyzoa   are    Retepora    (No. 

7 2 1 ,  R.  phoeniced)   and  Cristatella.     The  latter  has  the 
power  of  locomotion,  though  it  is    probably   descended 
from  some  marine  stationary  form. 


ANNELIDA. —  CHAETOPTERA. 

The  record  left  by  the  early  ancestors  of  our  present 
worms    is  scanty  and   unsatisfactory.     It  offers   another 

1  Hertwig,  Man.  Zool.,  transl.  by  J.  S.  Kingsley,  1902,  p.  323. 


METAZOA VERMES.  289 

illustration  of  the  fact  that  only  under  exceptional  condi- 
tions can  traces  of  soft-bodied  animals  be  preserved. 

Such  conditions  were  realized  in  Mesozoic  times  by 
the  peculiar  clay  of  the  present  lithographic  slates  of 
Bavaria,  the  extreme  fineness  of  which  made  it  possible 
for  an  impression  to  be  taken  and  preserved  of  even  so 
delicate  an  animal  as  a  jelly  fish.  The  Palaeozoic  forma- 
tions, however,  have  no  lithographic  slates,  and  the 
occasional  indefinite  trails  (PI.  722,  Nereites  cambrensis 
M'Leay),  the  filled-up  burrows  (PI.  723,  Planolites  vul- 
garis),  and  the  like,  are  but  uncertain  evidences  in  regard 
to  the  ancient  fleshy  progenitors. 

When,  however,  the  descendants  of  these  fleshy  ances- 
tors became  specialized  to  such  a  degree  as  to  possess 
masticating  organs  in  the  form  of  chitinous  jaws,  then 
these  hard  parts  would  be  preserved.  The  fact  that  such 
remains  (PI.  724,  figs,  i,  2,  jaws  of  Eunicites,  greatly 
enlarged1)  exist  in  the  lower  Palaeozoic  rocks  proves  that 
worms  originated  in  the  early  geologic  times.  Corrobo- 
rative testimony  on  this  point  is  given  by  Dr.  Hobb's 
discovery  of  worm  borings  and  worm  teeth  in  the  pre- 
Cambrian  rocks  of  eastern  Massachusetts.2 

Though  we  know  little  of  the  Palaeozoic  predecessors 
of  our  present  worms,  the  Bavarian  lithographic  slates 
help  us  greatly  in  regard  to  the  Mesozoic  ancestors. 
Remains  are  preserved  with  sufficient  clearness  to  enable 
us  to  determine  many  of  their  characteristics.  These 
worms  (PL  725,  fig.  i.  Eunicites  avitus  Ehl.),  had  long 
bodies  divided  into  a  large  number  of  segments  (more 
clearly  seen  in  fig.  2,  Ctenoscohx  procerus) .  The  greatest 
breadth  of  the  worm  is  at  the  anterior  end,  and  the  body 
tapers  towards  the  posterior  extremity  which  is  not  pre- 
served in  fig.  i,  but  is  seen  in  fig.  2.  On  either  side  of 


1  Most  of  these  jaws  do  not  average  more  than  one  twelfth  of  an 
inch  in  length. 

2  See  Amer.  Geol.,  XXIII,  Feb.,  1899,  p.  109. 


290  SYNOPTIC    COLLECTION. 

the  body  the  bristles  or  setae  are  distinctly  seen  (fig.  i), 
but  it  is  not  definitely  known  whether  these  worms  pos- 
sessed locomotive  paddles  called  parapodia.  The  jaws 
are  found  in  place  (fig.  i)  and  in  some  species  of 
Eunicites  (E.  dentatus,  fig.  3)  they  bear  prominent  teeth, 
reminding  one  of  the  toothed  jaws  of  the  Palaeozoic 
species,  Eunicites  simplex  H.  (PL  724,  fig.  i)  and  £. 
dintonensis  H.  (fig.  2). 

Doubtless  naked  worms  with  primitive  structural  fea- 
tures exist  or  have  existed  in  the  abyssinal  depths  of  the 
sea,  but  these  could  hardly  be  brought  to  the  surface  in 
perfect  condition.  Most  of  the  worms  so  far  obtained 
have  been  protected  by  a  tube,  and  are  specialized  by 
the  possession  of  numerous  organs.  There  is  evidence, 
furthermore,  that  many  of  these  forms  have  migrated 
from  shallow  water  to  the  deep  sea,  and  therefore  they 
possess  a  combination  of  adaptive  characters  which  ren- 
ders them  puzzling  and-  of  little  phylogenetic  value. 

In  default  of  fossils  representing  pre-Cambrian  or 
Cambrian  fleshy  forms,  and  of  primitive  deep-sea  species, 
we  should  naturally  turn,  as  we  have  done  already  in  sev- 
eral groups  under  similar  circumstances,  to  the  embry- 
onic and  larval  stages  of  development  of  a  primitive, 
marine,  and  free-swimming  member  of  the  class  under 
consideration. 

There  are  many  reasons  for  considering  Dinophilus  as 
a  primitive  worm,  although  its  development  has  not  been 
worked  out  in  detail  nor  the  trochophore  (if  one  exists) 
figured,  yet  the  young  stage  (PI.  726,  fig.  i,  D.  taeniatus} 
is  little  more  than  a  trochophore.  There  is  no  meta- 
morphosis, and  it  does  not  appear  that  the  larval  stages 
peculiar  to  those  forms  that  pass  through  a  metamorpho- 
sis are  skipped  in  the  development  of  this  worm.  We 
should  say,  on  the  contrary,  that  these  stages  have  never 
occurred  in  the  ancestors  of  Dinophilus  and  that  the 
embryo  develops  gradually  from  the  egg  to  the  young 
form  (fig.  i).  In  this  stage  the  body  is  transparent,  and 


METAZOA — VERMES.  291 

is  divided  into  a  few  distinct  segments.  Both  the  young 
and  the  adult  (fig.  2,  D.  gigas)  are  without  tentacles  and 
no  parapodia  are  developed.  Neither  are  setae  found, 
and  locomotion  is  effected  by  the  bands  of  cilia  clearly 
seen  in  figs,  i,  2.  Practically,  according  to  Harmer,1 
the  adult  is  a  trochophore,  or,  as  Benham2  puts  it,  "the 
adult  is  more  like  a  larval  Polychaete  than  a  full  grown 
worm." 

While  it  is  true  that  there  is  a  marked  difference  in 
size  between  the  male  and  the  female  of  some  species 
(which  is  one  reason  why  some  naturalists  consider 
Dinophilus  as  a  secondary  rather  than  a  primitive  form), 
nevertheless  there  are  other  species,  like  those  figured  in 
PL  726,  figs,  i,  2.  where,  excepting  the  sexual  organs 
proper,  the  sexes  are  alike. 

Most  Annelida  arise  from  a  trochophore  which  does 
not  differ  essentially  from  that  of  Mollusca.  As  we  have 
already  seen,  this  trochophore  stage  is  common  to  sev- 
eral groups  of  animals,  —  Pelecypods,  Gastropods,  Cephal- 
opods,  Pteropods,  Brachiopods,  —  and  for  this  reason  we 
maintain  that  it  must  be  of  phylogenetic  importance. 

When  the  ancestors  of  the  trochophore  which  were 
active  swimmers,  gave  up  this  mode  of  locomotion  and 
became  crawlers,  it  is  not  unlikely  that  the  body  elongated. 
Surely  it  is  not  difficult  to  conceive  that  such  a  change  of 
habitat  and  of  habit  would  produce  a  long,  more  or  less 
flattened  and  unsegmented  body.  Neither  is  it  hard  to 
see  that,  as  time  went  on  and  the  habit  of  creeping  was 
established,  it  would  be  an  immense  advantage  to  such  a 
crawling  animal  to  have  its  body  capable  of  the  greatest 
possible  freedom  of  motion.  This  freedom  might  be 
gained  through  purely  mechanical  means,  whereby  the 
sinuous  movements  of  the  body  would  bring  about  a  divi- 
sion into  parts  or  segments  of  greater  and  less  mobility. 

1  Joum.  Mar.  Biol.  Assoc.,  n.  s.,    I,  1889,  P-   I4I- 

2  Cambridge  Nat.  Hist.,  II,  1896,  p.  243. 


292  SYNOPTIC    COLLECTION. 

The  boundaries  of  the  segments  would  in  time  become 
definite  and  the  segments  themselves  be  capable  of  mov- 
ing freely  upon  one  another.  While  this  may  be  an 
explanation  of  the  origin  of  segmentation,  there  is  as  yet 
no  evidence  to  prove  it  in  embryology.  Granted,  how- 
ever, that  this  explanation  be  correct,  it  is  doubtful 
whether  the  flattened,  unsegmented  stage  of  development 
is  represented  by  adult  living  worms  of  to-day.  The 
unsegmented  Nemerteans  and  Turbellaria  (p.  317)  are 
considered  by  many  naturalists  as  the  nearest  living 
representatives  of  ancestral  forms,  but  there  are  so  many 
reasons  for  considering  these  as  secondary  and  not  primi- 
tive groups  (seep.  317)  that  we  prefer  to  place  them  as 
terminal  branches  rather  than  trunk  forms  of  the  great 
genealogical  tree  of  Vermes. 

The  process  by  which  at  the  present  time  a  many-seg- 
mented worm  arises  from  a  trochophore  is  shown  more 
plainly  in  Polygordius  than  in  any  other  worm  so  far 
described.  For  this  reason  we  shall  consider  it  here,  but 
provisionally,  since  it  is  not  yet  clear  whether  Polygordius 
is  a  primary  or  a  secondary  form.  As  a  rule  such  uncer- 
tain species  are  omitted  in  this  Guide,  and  an  exception 
is  made  in  favor  of  Polygordius  only  because  it  illustrates 
the  subject  far  better  than  any  other  known  worm.  Its 
trochophore,  familiarly  known  as  "Loven's  larva"  (PI. 
727,  fig.  i,  seen  from  the  side),  is  free-swimming  and 
similar  to  the  trochophore  of  Mollusca.  It  is  spherical 
and  transparent.  The  mouth  (fig.  i,  at  the  left)  is  on  the 
ventral  side  and  in  front  of  it  is  the  pre-oral  lobe,  and 
also  the  pre-oral  band  of  cilia.  Parallel  with  this  band, 
and  just  back  of  the  mouth,  is  another  band  of  cilia  which 
are  much  shorter  than  those  in  front.  This  band  is  seen 
more  plainly  in  fig.  2,  which  is  a  drawing  of  an  older  larva. 

The  digestive  system  consists  of  a  mouth,  stomach,  and 
intestine  ending  in  the  anus  which  is  at  the  posterior  end 
(figs,  i,  2).  Soon  the  trochophore  begins  to  elongate 
(fig.  3)  by  adding  segments  to  the  posterior  end,  while  the 


METAZOA VERMES.  293 

pre-oral  lobe  in  front  of  the  mouth  decreases  in  size  (fig. 
4) .  This  process  goes  on  until  the  form  of  the  mature 
larva  (fig.  5)  is  attained.  The  body  is  now  made  up  of 
similar  segments ;  the  mouth  is  on  the  ventral  side,  and 
there  is  an  ocellus  on  either  side  near  the  forward  end, 
while  it  possesses  (in  addition  to  the  young  larva)  a  pair 
of  short  tentacles  (fig.  5).  These  are  its  only  appendages, 
and  as  there  are  no  locomotive  organs  in  the  form  of 
chitinous  setae  or  fleshy  paddles,  the  animal  moves  by 
means  of  cilia  only.  Neither  does  this  worm  possess 
external  breathing  organs  in  any  form,  for  the  skin  proba- 
bly performs  the  work  of  respiration. 

The  adult  (PI.  728,  fig.  i,  natural  size  ;  fig.  2,  enlarged) 
does  not  differ  essentially  from  the  mature  larva.  Some 
of  its  features  enlarged  are  shown  in  figs.  3-5.  The  body 
is  segmented,  the  segments  showing  more  plainly  in  the 
enlarged  section  (fig.  3)  than  in  figs.  1,2.  The  pre-oral 
lobe  bears  the  pair  of  hairy  tentacles  (fig.  4)  and  back  of 
this  lobe  is  the  mouth  (fig.  4).  The  anus  is  still  at  the 
posterior  end  of  the  body  (fig.  5)  surrounded  by  a  circle 
of  papillae. 

The  worms  which  are  best  known  and  which  are  exhib- 
ited in  the  Synoptic  Collection  belong  for  the  most  part 
to  one  of  two  groups.  Either  they  are  broadly  differenti- 
ated by  the  possession  of  many  parts  and  organs,  or  they 
are  extremely  specialized  by  the  reduction  of  organs. 
The  first  group  to  be  described  consists  mainly  of  marine 
and  shallow-water  forms,  and  many  are  found  for  a  longer 
or  shorter  time  under  stones  or  burrowing  in  sand.  They 
have  become  more  or  less  adapted  to  their  environment, 
so  that  some  of  their  organs  are  secondarily  acquired  and 
these  of  course  throw  little  light  on  phylogenetic  relation- 
ships. The  second  group,  however,  consists  mostly  of 
parasites,  and  their  structure  has  undergone  such  a  pro- 
found modification  that  they  are  much  farther  removed 
from  the  primitive  ancestral  forms  than  are  the  members 
of  the  first  group.  They  have  become  adapted  to  the 


294       .  SYNOPTIC    COLLECTION. 

most  varied  situations,  and  their  organs  have  passed 
through  such  a  complete  change  that  they  are  of  no  phy- 
logenetic  value. 

Aphrodite  or  the  "sea-mouse"  (No.  729)  belongs  to 
the  first  group.  It  is  unique  in  possessing  an  almost  in- 
numerable number  of  delicate  hairs  and  larger  setae, 
which  reflect  the  most  brilliant  prismatic  hues,  making 
the  worm  a  marvel  of  beauty.  Alcohol  has  no  power  to 
rob  this  animal  of  its  gorgeous  tints.  The  mechanical 
cause  for  the  coloring  lies  in  the  extremely  fine  lines  on 
the  surface  of  the  hairs  which  break  the  light  into  its 
component  elements,  but  the  reason  for  the  file-like  sur- 
face and  the  "forest  of  prisms"  is  not  so  clear,  especially 
as  it  is  said  that  these  worms  are  usually  covered  with 
clay  so  that  their  beauty  is  hidden  from  the  sight  of  other 
animals. 

No.  730  is  a  preparation  of  Aphrodite  showing  the 
scale-like  respiratory  organs.  These  are  situated  on  the 
back  of  the  worm  and  are  protected  by  a  felting  of  hair 
(see  No.  729).  The  water  passes  through  the  felting 
and  bathes  the  scales,  after  which  it  is  expelled  from  the 
posterior  end. 

A  relative  of  Aphrodite  is  found  in  the  scale-bearer 
Phyllodoce  (PI.  731,  P.  maculata  Oersted).  The  young 
larva  (fig.  i  ;  fig.  2,  side  view  of  the  same)  has  a  band  of 
cilia  and  the  body  is  segmented.  Gradually  the  worm 
lengthens  (fig.  3  ;  fig.  4,  ventral  view  of  same),  the  pad- 
dles become  distinct  and  also  the  setae,  though  the  cilia 
still  persist.  The  tentacles  grow  out  and  the  large  mouth 
(fig.  4)  is  back  of  the  band  of  cilia.  The  body  continues 
to  grow  longer  (fig.  5).  The  head  now  possesses  eight 
tentacles,  as  in  the  adult  (fig.  6). 

Sigalion  squamatum  (No.  732)  is  also  provided  with 
scales  on  many  of  the  segments.  This  is  such  a  peculiar- 
looking  worm  that  at  first  sight  it  seems  as  though  the 
body  wall  had  been  removed  exposing  the  internal  organs 
and  that  these  consisted  of  a  long,  double,  vertebral  rod 


METAZOA VERMES.  295 

with  an  infinite  number  of  brush-like  setae  attached  on 
either  side  and  enclosing  laterally  a  double  row  of  deli- 
cate leaf-like  parts.  In  reality,  the  long  double  rod  is  the 
ventral  side  of  the  worm,  and  the  leaf-like  parts  are  scales 
or  peculiar  modifications  of  the  dorsal  surface.  In  this 
case,  gills  exist  with  the  scales.  The  head  is  differenti- 
ated from  the  body.  Its  anterior  portion  including  the 
slit-like  mouth  is  dark  brown  in  color,  indicating  that  it 
performs  hard  work. 

Psammolyce  arenosa  (No.  733)  covers  the  upper  part  of 
its  body  with  coarse  sand,  so  that  at  first  sight  there 
appears  to  be  a  protecting  tube.  The  under  side,  how- 
ever, is  not  covered  in  this  way  so  that  the  median  groove 
of  the  body  is  distinct  and,  in  lesser  degree,  the  sutures 
between  the  segments.  Clusters  of  setae  extend  down 
both  sides  of  the  body  and  are  useful  in  locomotion. 

The  species  of  Nereis  are  typical  members  of  the  group 
of  shallow-water  worms.  The  larva  of  an  undetermined 
species  is  seen  in  PI.  734,  fig.  i.  At  this  early  stage  it 
is  transparent  and  consists  of  a  few  distinct  segments. 
The  head  (figs,  i,  2)  is  provided  with  five  pairs  of 
appendages  and  three  pairs  of  eyes.  The  large,  toothed 
mandibles  (figs,  i,  2)  are  well  developed,  and  even  in 
this  early  period  they  can  be  seen  distinctly  through  the 
body  wall.  The  setae  are  prominent,  but  the  parapoclia 
have  not  yet  taken  on  the  form  peculiar  to  the  full  grown 
animal.  Although  the  adult  Nereis  virens  Sars  (No.  735  ; 
PI.  736,  figs.  1-4),  makes  a  loose  flexible  tube  for  itself1 
by  fasteninig  grains  of  sand  together  with  a  secretion  of 
its  body,  it  never  attaches  itself,  but  is  extremely  active, 
burrowing  in  sand  during  the  day  and  often  swimming  at 
night.  The  body  is  made  up  of  numerous  segments  of 
which  the  forward  ones  are  differentiated  into  a  head  (PI. 
736,  fig.  i).  This  part  in  this  species  bears  six  pairs  of 
tentacles  and  two  pairs  of  eyes  (fig.  i).  The  mouth  con- 

1  Trans.  Conn.  Acad.  Arts  and  Sci.,  Ill,  1878,  p.  265. 


296  SYNOPTIC    COLLECTION. 

tains  a  sac  called  a  proboscis  (fig.  2)  which  can  be  turned 
outward  as  seen  in  the  figure.  It  is  armed  with  many 
fine  horny  teeth  and  two  stout  hooked  teeth  already  seen 
in  the  larva. 

Along  each  side  of  the  body  there  is  a  row  of  fleshy, 
un jointed,  and  two-lobed  organs,  the  parapodia  (figs,  i,  3, 
4)  which  are  continuations  of  the  body  wall  (fig.  4). 
They  serve  as  efficient  paddles  in  locomotion,  and  the 
lobes  are  also  differentiated  into  breathing  organs.  In 
the  living  worm  these  lobes  are  bright  red  in  color,  owing 
to  the  blood  contained  in  them.  Extending  beyond  the 
edge  of  the  paddles  are  horny  setae  (fig.  3)  which  in  real- 
ity originate  within  the  body  cavity  and  pass  outward  pierc- 
ing the  body  wall  (fig.  4).  The  division  of  the  body  cav- 
ity into  segments,  which  is  one  of  the  chief  characteristics 
of  worms,  is  well  shown  in  fig.  3,  representing  the  forward 
end  of  Nereis  with  the  proboscis  in  place.  The  dorsal 
part  of  the  body  wall  has  been  removed  so  that  six  mus- 
cular partitions  are  exposed,  dividing  the  cavity  trans- 
versely into  as  many  compartments.  There  is,  moreover, 
a  marked  tendency  towards  the  repetition  of  the  paired 
organs  in  each  compartment,  such  as  the  nephridia,  the 
bundles  of  muscles,  and  the  ganglia  of  the  nervous  system. 

The  relative  position  of  the  three  important  systems  of 
organs  in  this  class  of  animals  is  shown  in  PI.  736,  fig.  4. 
The  digestive  system  represented  by  the  large  central 
circle  takes  up  the  greater  part  of  the  body.  Immediately 
above  and  below  it  are  the  long  tubes  of  the  circulatory 
system,  cut  across  in  fig.  4.  Below  the  ventral  blood 
vessel  is  the  nerve  cord  which  runs  the  whole  length  of 
the  body. 

Autolytus  cornutus  Ag.,  (PI.  737.  figs.  1-13),  is 
especially  interesting  as  it  is  one  of  the  few  worms  that 
illustrates  alternation  of  generations.  The  eggs  pass  from 
the  body  cavity  of  the  mother  into  a  bag  or  pouch  which 
has  grown  out  from  the  lower  side  of  her  body.  Here 
they  remain  and  are  brooded  over  by  the  parent  until  the 


METAZOA — VERMES.  297 

embryos  hatch;  the  pouch  then  breaks,  and  the  larvae 
are  set  free. 

The  larva  just  after  hatching  (fig.  i)  has  a  flattened, 
unsegmented  body  which  shows  no  differentiation  into 
regions.  Very  soon,  however,  the  beginnings  of  segments 
(fig.  2)  are  visible,  and  the  head  is  marked  off  by  a  slight 
constriction.  The  segments  become  more  apparent  (fig. 
3)  and  the  three  regions  are  clearly  marked  (fig.  4).  The 
tentacles  bud  out  (fig.  5)  and  the  bristles  grow  from  the 
middle  region  (fig.  6).  The  tentacles  increase  in  size  and 
the  setae  in  number  (fig.  7).  Later  the  posterior  organs, 
known  as  cirri,  grow  longer  (figs.  8,  9).  The  mature 
asexual  form,  called  the  "parent-stock,"  is  represented  in 
fig.  10.  It  multiplies  either  by  division  or  by  budding. 
If  by  the  former  process  the  anterior  end  remains  asexual 
while  the  posterior  end  develops  into  either  a  male  (fig. 
n,  male  ready  to  separate  from  parent-stock;  fig.  12,  for- 
ward part  of  a  male)  or  a  female  (fig.  13).  Larger  draw- 
ings of  the  mature  Autolytus  are  framed  and  placed  over 
the  Section.  The  figure  on  the  left  represents  the 
asexual  parent  stock  dividing  in  two;  the  middle  figure 
is  the  female  with  the  egg-bag,  and  the  figure  on  the  right 
the  free  male.  These  two  sexually  mature  individuals 
produce  the  fertilized  egg  which  in  turn  develops  into  the 
sexless  parent  stock  (fig.  10).  The  latter  produces  more 
than  one  offspring,  for  after  this  has  left,  the  anterior  end 
buds  out  new  segments  until  a  posterior  part  is  formed 
which  in  time  is  ready  to  be  thrown  off  and  to  develop 
into  either  a  male  or  a  female.  . 

Autolytus  is  placed  with  the  free-swimming  forms  since 
the  adult  male  and  female  are  found  at  the  surface  of  the 
sea.  The  parent  stock  also  is  free-swimming  when  the 
sexual  individual  is  attached  to  it.  At  other  times  it 
makes  a  delicate  tube  which  it  leaves  at  will. 

The  development  of  Autolytus  which  we  have  just  traced 
is  exceptional  in  one  particular,  namely,  in  the  flattened, 
unsegmented  state  of  the  very  young  larva.  In  conse- 


298  SYNOPTIC    COLLECTION. 

quence  of  this  early  condition,  it  may  be  urged  that  here 
is  a  proof  of  the  descent  of  the  segmented  Annelids  from 
the  group  of  flat,  unsegmented  worms. 

We  must  not  lose  sight  of  the  fact,  however,  that  this 
unsegmented  larval  state  is  accompanied  by  a  specialized 
mode  of  reproduction,  as  already  shown.  The  formation 
of  a  pouch  for  the  young,  the  brooding  by  the  mother, 
the  various  changes  in  the  development  of  the  asexual  and 
sexual  individuals,  all  indicate  secondary  instead  of  pri- 
mary conditions,  so  that  it  seems  most  probable  that  this 
flattened  state  of  the  young  larva  is  an  adaptive  character. 

The  proboscis  which  we  have  seen  in  Nereis  is  some- 
times of  great  size,  as  in  Rhynchobolus  siphonostoma  (No. 
738),  a  large,  distinctly  segmented  worm.  In  this  finely 
preserved  specimen  the  proboscis  is  extended  and  the 
four  dark  horny  teeth  are  seen  at  the  swollen  anterior  end. 
One  row  of  tiny  parapodia  with  setae  extending  from  them 
is  seen  on  either  side  of  the  body. 

Some  of  the  worms  of  this  group  of  Chaetopods  have 
the  head  so  slightly  differentiated  that  the  two  ends  of  the 
body  resemble  each  other,  as  in  Eteone  siphonodonta  (No. 
739).  They  are  tapering  and  terminate  in  a  blunt  point ; 
the  forward  end,  however,  differs  from  the  posterior  in 
having  short  tentacles. 

The  locomotive  organs  in  Eteone  are  prominent,  con- 
sisting of  a  double  row  on  each  side  of  the  body.  The 
upper  and  longer  organs  end  in  flattened  leaf-like  parts, 
while  the  lower  have  clusters  of  setae.  These  enable  the 
worm  to  move  swiftly  through  moist  sand  and  also  to 
penetrate  clay  and  fissures  in  rocks.  . 

Another  worm  with  an  inconspicuous  head  is  Halla 
parthenopeja  (No.  740),  which  is  of  great  size  with  a  large 
number  of  apparent  segments.  Florence  Buchanan  x  has 
shown  that  in  a  few  Annelida  (Chaetopods)  cases  occur 
of  intercalation  of  half  segments  and  of  spiral  segmenta- 

1  Quart.  Journ.  Micr.  Sci.,  XXXIV,  1893. 


METAZOA  —  VERMES.  299 

tion,  which  are  probably  variations  from  the  normal  seg- 
mentation. This  variation  of  a  spiral  segmentation  is 
illustrated  by  Halla,  and  since  it  occurs  in  Oligochaeta 
(see  p.  305)  and  in  Cestodes,  especially  in  Bothriocephalus 
latus^  it  indicates  a  tendency  toward  secondary  and  adap- 
tive specialization.  Both  the  upper  and  lower  surfaces  of 
Halla  are  iridescent.  On  either  side  are  the  parapodia 
with  bunches  of  projecting  setae. 

Besides  the  species  of  worms  already  described  as  free- 
swimmers  there  are  many  others  which  are  free-swimming 
when  young,  but  which  later  in  life  make  tubes  and  fasten 
them  to  foreign  objects  either  temporarily  or  permanently. 
Although  the  worms  are  never  organically  connected 
with  the  tubes,  yet  most  remain  in  them  for  the  greater 
•  part  of  the  time,  and  in  this  new  position  develop  struc- 
tural characters  fitting  them  for  a  sedentary  life. 

These  worms  are  usually  grouped  together  under  the 
name  of  the  Sedentaria  in  contrast  to  the  Errantiaor  free- 
swimming  forms.  It  must  be  borne  in  mind,  however, 
that  there  is  no  sharp  line  of  demarcation  between  these 
groups,  since  some  Errantia  (Eunicidae,  some  Polynoids). 
make  tubes  and  some  Sedentaria  are  tubeless  (Poly- 
cirrus).  Broadly  speaking,  nevertheless,  the  division 
holds  good,  and  the  Sedentaria,  having  acquired  many 
secondary  characters,  are  naturally  placed  after  the 
Errantia. 

One  of  these  sedentary  worms  is  Arenicola  marina 
Linn.  (No.  741,  model).  Although  not  permanently 
settled,  Arenicola  makes  a  U-shaped  tunnel  for  itself  in 
the  sand  and  remains  in  it  much  of  the  time.  The  para- 
podia  not  being  needed  have  disappeared,  and  the  ante- 
rior segments  bear  setae  only.  The  central  segments  are 
provided  with  setae  and  gills;  the  latter  are  protected  in 
some  degree  by  the  setae  that  extend  beyond  them,  and 
also  by  the  swollen  anterior  end  of  the  body  which 

1  Buchanan,  loc.  ctt.,  p.  541. 


300  SYNOPTIC    COLLECTION. 

enlarges  the  burrow  as  the  animal  moves  along.  Fur- 
thermore, this  burrow  is  lined  with  a  mucous  secretion  from 
the  body  which  soon  hardens  so  that  the  sand  does  not 
come  in  contact  with  the  gills  while  the  worm  is  in  its 
home. 

Since  Arenicola  digs  its  own  tunnel  it  could  not  have 
the  delicate  gills  on  the  segments  near  the  mouth,  but  the 
anterior  region  in  many  of  these  tube  inhabiting  worms 
is  provided  with  a  profusion  of  long,  slender  feelers  and 
branchiae,  while  in  the  middle  and  posterior  parts  of  the 
body  only  a  few  of  these  organs  occur.  This  is  the  case 
with  Audouinia  filigera  (No.  742),  a  handsome  and  grace- 
ful worm.  Extending  the  whole  length  of  the  body  of 
this  Annelid  are  four  rows  of  setae. 

Most  curious  of  all  this  group  of  worms  is  Chaetop- 
terus  variopedatus  Ren.  (No.  743).  It  never  leaves  its 
tube  l  and  therefore  its  body  has  become  modified  in 
various  ways.  The  outer  skin  is  delicate  and  light  col- 
ored. The  segments  and  fleshy  appendages  of  the  middle 
and  anterior  regions  of  the  body  are  more  specialized 
than  those  of  the  posterior  region,  since  it  is  these  that 
are  modified  for  the  purposes  of  catching  food  and  for 
holding  the  animal  in  its  tube.  As  Chaetopterus  does 
not  require  locomotive  paddles  and  setae,  these  organs 
are  not  developed,  though  there  are  stiff  hairs  and  plates 
which  aid  the  animal  in  moving  up  and  down  its  tube. 

Terebella  (=Amphitrite)  coiichilega  Pall.,  is  naked  and 
free-swimming  when  young  (No.  744  a-c).  There  is  no 
marked  differentiation  of  the  body  in  these  stages,  but 
the  appendages  are  developed  in  the  form  of  clusters  of 
setae  on  either  side.  The  mouth  opens  on  the  ventral 
side  (b)  and  in  front  of  it  is  developed  a  very  long  feeler 
(b,  c).  Other  feelers  grow  out  (c)  until  in  the  adult  (No. 
745,  model)  there  are  many  of  these  delicate  organs 
besides  bushy  branchiae  ;  the  latter  are  usually  red  (as 

1  Benham,  Cambridge  Nat.  Hist.,  II,  1896,  p.  323. 


METAZOA VERMES.  301 

represented  by  the  model),  owing  to  the  blood  contained 
in  them.  The  tube  (No.  745)  of  the  adult  Terebella  is 
sometimes  fifteen  inches  long  and  is  usually  made  of 
fragments  of  shells,  sand  grains,  etc.,  cemented  together 
by  a  secretion  of  the  body.  These  substances  the  worm 
prefers,  and  it  shows  discrimination  in  selecting  materials, 
refusing  certain  substances  altogether,  as  pointed  out  by 
Dalyell.1  From  the  larger  end  the  many  extremely  long 
feelers  and  the  feathery,  brilliantly  colored  gills  are 
extended,  as  already  stated ;  the  latter  are  borne  on  only 
a  few  of  the  anterior  segments.  One  of  the  tentacles 
has  become  differentiated  into  anoperculum  or  "stopper" 
which  closes  the  tube  in  time  of  danger. 

The  bristles  are  found  on  the  forward  segments  only, 
having  disappeared  from  the  posterior  region  of  the  body 
where  they  would  be  of  no  use  to  a  tube-inhabiting  animal. 

Stylarioides  monilifer  (No.  746),  is  an  instructive  form. 
The  plump,  rounded,  anterior  region  of  the  body  has 
nearly  lost  the  boundary  lines  of  the  segments,  though 
these  are  distinct  on  the  tapering  posterior  region.  The 
head  is  extremely  differentiated.  The  tentacles  are  sur- 
rounded by  long  bristles  which  reflect  the  most  brilliant 
prismatic  hues.  Many  of  the  setae  on  the  anterior  region 
of  the  body  exist  as  vestiges  like  the  lines  of  demarcation 
between  the  segments,  while  the  setae  on  the  posterior 
region  are  more  regular  and  bushy. 

Cistenides,  or  as  it  was  formerly  called,  Pectinaria  (No. 
747),  has  a  symmetrical  tube  reminding  one  in  shape 
of  the  shell  of  Dentalium  (see  No.  534).  It  is  made 
of  tiny  pebbles  which  are  fitted  together  with  extreme 
neatness.  There  is  an  opening  at  the  smaller  posterior 
extremity,  and  the  head  extends  from  the  larger  anterior 
end ;  this  is  provided  above  with  prismatic  bristles. 
Though  placed  with  the  Sedentaria,  Cistenides  is  not  a 
sedentary  worm,  since  it  travels  about  freely,  carrying 
its  tube  with  the  smaller  end  pointing  upward. 

1  Ann.  and  Mag.  Nat.  Hist.,  (6),  XIII,  1894,  p.  n. 


302  SYNOPTIC    COLLECTION. 

A  worm  that  buries  its  long  quill-shaped  body  with  the 
exception  of  a  few  of  the  anterior  segments  is  Sabella 
penicillus  Linn.  (No.  748,  model).  Its  tube  is  leathery,  and 
is  formed  by  a  secretion  of  the  body  ;  from  its  opening  the 
branching  gills,  which  are  supported  by  a  cartilaginous 
skeleton,  are  extended.  The  model  shows  the  animal  out 
of  its  slender  tube,  so  that  the  body  with  its  setae  and 
parapodia  as  well  as  its  long,  delicate  branchiae  and 
tentacles  can  be  clearly  seen. 

Many  of  these  tube-inhabiting  worms  have  large,  seg- 
mented bodies,  while  the  paddles  and  setae  are  more  or 
less  reduced  in  size.  Such  a  worm  is  Spirographis 
spallamani  (No.  749),  in  which  these  lateral  appendages 
are  tiny.  The  feelers,  on  the  other  hand,  are  active 
working  organs  and  are  finely  developed. 

Two  tubes  of  Branchiomma  koellikeri  (No.  750),  are 
shown  in  No.  751.  One  is  made  of  sand  and  tiny 
pebbles;  it  is  symmetrical  and  well  put  together.  The 
other  is  composed  of  similar  materials  throughout  about 
three  fourths  of  its  length,  but  the  remaining  fourth  has 
pieces  of  rock  of  surprising  size  incorporated  in  it.  Its 
extreme  irregularity  reminds  one  of  the  experimental 
work  in  shell-making  seen  among  the  Protozoa  (see 
Saccammina,  PI.  15),  and  sponges  (Prophysema,  PL  60). 
It  is  remarkable  that  the  cementing  material  is  sufficiently 
strong  to  hold  these  fragments  in  place,  especially  as  only 
a  small  portion  of  their  surface  is  in  contact  with  the 
tube.  From  the  anterior  end  of  the  tube  many  delicate 
tentacles  are  put  forth.  Along  each  side  are  short  setae 
without  paddles.  According  to  M'Intosh  x  one  species  of 
this  genus,  Branchiomma  vesiculosum,  has  the  surface  of 
the  greatly  enlarged  eye  minutely  dotted  as  if  furnished 
with  corneal  facets  analogous  to  those  of  Crustacea  and 
Insecta ;  the  eye  has  proximally  a  kind  of  peduncle. 

The  tubes  already  described  have  been  formed  mechani- 

1  Chall.  Rep.,  Zool.,  XII,  1885,  p.  494. 


METAZOA  —  VERMES.  303 

cally  by  the  animal  picking  up  such  materials  as  it  could 
find  and  working  them  over;  but  the  tubes  of  Serpula 
(No.  752,  S.  contortuplicata),  are  made  by  a  chemical 
process  and  are  composed  wholly  of  carbonate  of  lime. 

In  this  genus  the  setae  are  reduced  in  size.  The  gills 
(see  No.  752)  are  borne  on  the  forward  segments  of  the 
body  and  can  be  withdrawn  into  the  tube,  while  the  open- 
ing is  closed  by  a  tentacle,  the  end  of  which  has  become 
differentiated  into  an  operculum. 

The  habit  of  living  attached  and  in  chemically  formed 
tubes  was  acquired  by  some  genera  very  early  in  geologic 
times.  The  Palaeozoic  formations  yield  specimens  of 
Spirorbis  which  resemble  those  living  to-day  (PI.  753, 
Spirorbis  omphalodes  Goldf.).  Usually  in  these  fossils 
the  tube  is  hollow  throughout,  but  sometimes  the  shell  is 
divided  into  a  few  chambers  by  limy  walls.  Not  only  do 
tightly  coiled  forms  occur  as  represented  by  PL  753,  but 
some  species,  like  Spirorbis  laxus  (PL  754,  figs.  1-4), 
exhibit  old  age  or  gerontic  characters.  The  worm  on 
reaching  maturity  (PL  754,  figs,  i,  2)  begins  to  untwist 
(fig.  3)  and  in  rare  cases  this  process  goes  on  until  the 
whole  tube  is  uncoiled  excepting  the  apical  portion  (fig. 
4).  It  is  interesting  to  note  that  the  round  aperture  of 
this  tube  is  smaller  than  in  the  mature  or  ephebic  shell 
(figs.  2,  3)  which  we  have  already  seen  is  the  case  in 
certain  gerontic  stages  of  Cephalopods  (see  Nos.  617, 
6 1 8).  The  descendants  of  Spirorbis  are  found  living 
to-day  in  great  numbers. 

The  larva  of  Spirorbis  spirillum  Gould  (PL  755,  figs,  i, 
2),  is  free-swimming  at  first,  but  only  for  a  few  hours. 
It  then  settles  down  and  begins  to  build  its  tube.  The 
tentacles  and  setae  develop  early  (fig.  3),  the  former 
branch  rapidly  and  one  becomes  specialized  into  an 
operculum  (fig.  4,  p).  Thus  it  is  seen  that  the  tendency 
towards  the  sedentary  habit  is  inherited  so  early  in  the 
life  of  the  individual  that  the  young  Spirorbis  (fig.  4) 
completes  its  development  within  the  tube.  This  ex- 


304  SYNOPTIC    COLLECTION. 

plains  why  the  posterior  region  of  the  body  is  small  and 
without  well  developed  appendages. 

The  adults  are  often  attached  to  seaweed  by  one  side 
of  the  shell  (No.  756,  S.  nautiloides  Lam.  ;  No.  757,  S. 
lucidus} .  An  examination  of  this  large  settlement  (No. 
757)  shows  a  great  variation  in  the  tube.  If  one  were 
unfamiliar  with  fossil  forms,  it  would  seem  as  if  here  was  a 
spiral  shell  in  process  of  making ;  as  if,  in  short,  a  straight 
tube  coiling  round  the  delicate  stem  of  an  alga  became  in 
time  a  loose  spiral.  When,  however,  one  observes  that 
as  a  rule  the  young  tube  at  the  apex  is  closely  coiled,  as 
we  have  seen  in  the  specialized  fossil  species  (PI.  753), 
and  that  it.  is  the  adult  stage  which  is  usually  straight, 
then  one  sees  he  is  dealing  with  secondary  and  not  with 
primitive  conditions.  The  spiral  of  the  young  tube  in 
S.  lucidus  and  S.  laxus  is  doubtless  inherited  from  spiral- 
tubed  ancestors,  but  the  tendency  to  coil  loosely  around 
stems  is  evidently  an  adaptation  to  surroundings.  This 
view  is  strengthened  by  the  fact  that  those  specimens  of 
Spirorbis  which  are  found  on  the  flat  fronds  of  the  Fucus 
(No.  756)  are  seldom  if  ever  uncoiled  to  such  a  degree 
as  those  upon  stems. 

On  a  small  specimen  of  Fucus  we  have  seen  upwards 
of  three  thousand  tubes  of  Spirorbis  (2,800  were  actually 
counted,  and  there  were  a  few  hundred  more  in  the  hol- 
lows) not  one  of  which  was  uncoiled.  The  whorls  of 
the  close  spiral  of  the  young  tubes  could  be  traced  from 
the  inside  in  many  places,  where  only  a  portion  of  the 
tube  had  been  broken  away  owing  to  the  strength  of  the 
cement  by  which  it  was  fastened  to  the  Fucus. 

The  breathing  organs  of  the  living  Spirorbis  extend 
from  the  opening  of  the  tiny  coiled  tube  (No.  756),  and 
are  protected  when  within  the  tube  by  the  operculum 
(also  seen  in  No.  756). 


METAZOA VERMES.  305 

ANNELIDA. —  OLIGOCHAETA. 

Transitional  forms  between  the  marine  Chaetopoda 
and  the  terrestrial  Oligochaeta  may  be  represented  by 
Manayunkia  speciosa  Leidy.  This  little  tube-worm  in- 
habits fresh  water,  while  at  the  same  time,  according  to 
its  discoverer,  it  is  related  to  the  marine  worms,  especi- 
ally to  Fabricia,  a  near  ally  of  Terebella. 

In  the  development  of  Manayunkia  the  free-swimming 
stage  is  skipped  and  even  the  embryo  (PI.  758,  figs.  2,  3) 
that  develops  from  the  egg  (fig.  i)  has  lost  its  cilia.  The 
different  stages  of  the  larva  (figs.  4-6)  are  passed  within 
the  tube,  and  thus  the  young  are  "retained  under  the 
care  of  the  parent  until  sufficiently  developed  to  be  able 
to  care  for  themselves."  1  Both  larvae  and  adult  (fig.  70 
are  divided  into  a  small  number  of  segments.  The  adult 
is  abundantly  supplied  with  tentacles.  There  are  no 
parapodia,  but  each  segment  is  provided  on  either  side 
with  a  cluster  of  setae.  These  organs  are  small  and 
generally  few  in  number,  as  compared  with  the  numerous 
strong  bristles  of  Chaetopods  ;  hence  the  name  of  Oligo- 
chaeta. 

The  terrestrial  Oligochaeta  are  represented  by  the 
common  earthworm,  Lumbricus  terrestris  Linn.  (Nos. 
759'  760).  Although  a  land  animal,  it  is  able,  according 
to  Romanes  2  to  live  in  water  nearly  four  months. 

The  eggs  of  the  earthworm  are  laid  in  cocoons  or  egg- 
cases  and  the  free-swimming  larval  stages  are  wholly 
skipped,  so  that  the  worm  acquires  the  form  of  the  adult 
before  leaving  the  egg. 

The  peculiar  iridescence  already  observed  on  marine 
worms  is  well  seen  when  the  earthworm  is  immersed  in 
water  and  placed  in  the  sunshine. 

1  Leidy,  Proc.  Acad.  Nat.  Sci.  Phila.,  1883,  p.  209. 
'Nature,  XXIV,  1881,  p.  553. 


306  SYNOPTIC    COLLECTION. 

The  body  is  segmented.  Late  in  life x  each  segment 
may  become  ringed,  making  it  difficult  to  determine  the 
exact  number  of  segments,  but  the  secondary  rings  are 
superficial,  not  being  represented  by  muscular  partitions 
in  the  body  cavity. 

The  two  ends  of  the  body  are  similar,  since  the  forward 
end  is  not  differentiated  into  a  head  and  there  are  no 
tentacles  nor  eyes.  The  mouth  leads  into  a  proboscis 
which  is  not  armed  with  teeth. 

The  worm  is  well  supplied  with  locomotive  organs  in 
the  form  of  hooked  setae  which  extend,  with  the  excep- 
tion of  a  few  segments,  in  four  double  rows  from  one  end 
of  the  body  to  the  other. 

The  structure  of  the  earthworm  is  an  illustration  of 
specialization  by  the  suppression  of  parts.  The  cause 
for  this  suppression  is  found  in  the  habits  of  the  animal. 
No  longer  swimming  freely  in  the  sea  like  its  early  ances- 
tors, it  has  for  some  reason  or  other  taken  to  crawling 
through  the  earth.  In  such  a  situation  what  use  is  there 
for  paddles,  eyes,  or  tentacles  ?  Eating  soft,  partly  de- 
cayed organic  matter  in  the  earth,  what  use  has  the  worm 
for  horny  teeth  like  those  of  its  marine  relative,  the 
greedy  Nereis  ? 

The  forward  end  of  the  body  is  pointed  for  tunneling, 
and  the  setae  with  the  supplementary  muscles  can  easily 
pull  the  long  body  through  the  earth.  Thus  the  worm  is 
adapted  to  its  environment  and  it  is  seen  that  the  adap- 
tive organs  are  secondarily  acquired. 

The  earthworm  is  an  hermaphrodite,  although  self-fer- 
tilization does  not  take  place.  The  worms  mate  and  the 
breeding  season  is  indicated  by  the  swollen  clitellum  or 
saddle  (see  No.  759  and  also  No.  760,  specimen  on  the 
right;  these  preparations  were  made  according  to  Sem- 
per's  method).  The  development  is  accelerated  as  we 
have  shown,  and  in  this  way  the  Oligochaeta  differ  from 
the  Chaetopoda. 

1  Cambridge  Nat.  Hist.,  II,  1896,  p.  394. 


METAZOA VERMES.  307 


ANNELIDA.  —  HIRUDINIA. 

Some  of  the  non-parasitic  members  of  this  class  resem- 
ble the  Oligochaeta.  Nephelis  (PL  761,  the  young),  for 
example,  is  cylindrical  in  form  similar  to  the  earthworm, 
and  its  suckers  are  smaller  than  in  most  members  of  its 
class.  Its  intestine  is  not  differentiated  into  numerous 
large  sacs  as  is  the  case  with  the  more  specialized  Hiru- 
dinia  to  be  hereafter  described. 

The  eggs  of  Nephelis  are  deposited  in  cocoons  in 
fresh  water,  but  the  adults  often  leave  the  water  and  live 
under  stones  on  the  shore.1 

The  land  leech,  Haemadipsa  japonica  (PI.  762,  fig.  i, 
at  rest,  dorsal  view;  fig.  2,  ventral  view;  fig.  3,  another 
worm  stretched  out,  dorsal  side  ;  all  natural  size),  lives 
in  moist  places  among  mountains  and  never  goes  to  the 
water,  not  even  to  lay  its  eggs.  As  in  all  leeches  the  seg- 
ments are  ringed,  making  it  difficult  to  determine  the 
exact  number  (fig.  4,  posterior,  and  fig.  5,  anterior  end, 
both  figures  enlarged).  A  shortening  of  the  body  at 
either  end  has  taken  place  in  Haemadipsa,  as  in  most 
land  leeches,  brought  about  by  a  reduction  of  the  number 
of  rings  in  a  segment. 

The  eggs  of  the  European  medicinal  leech,  Hirudo 
medicinalis  Linn,  (in  America,  Macrobdella  decora  Say,  No. 
763,  is  often  used  in  place  of  Hirudo),  are  laid  in  cocoons 
which  are  placed  in  holes  that  the  mother  has  made 
above  water  level  in  the  soft,  moist  banks  of  the  pond 
she  inhabits.  The  cocoon  usually  contains  about  twenty 
eggs  and  is  filled  with  albumen.  The  young  remain  in 
the  cocoon,  feeding  upon  the  food  prepared  for  them  until 
they  have  attained  the  form  of  the  parent.  The  free- 
swimming  larval  stage  is  therefore  omitted,  so  that  the 
development  is  accelerated. 

1  Johnston,  Cat.  Worms  Brit.  Mus.,  1865,  p.  43. 


308  SYNOPTIC    COLLECTION. 

The  segments  of  the  adult  are  obscured,  the  secondary 
annular  markings  obliterating  the  division  lines  of  the 
true  segments.  Paddles  and  setae  are  not  developed  in 
Hirudo,  the  animal  either  swimming  by  means  of  the  thin 
edges  of  its  body  or  crawling  by  aid  of  its  suckers.  It 
is,  however,  a  sluggish  creature,  so  that  it  often  remains 
attached  by  its  suckers  for  a  long  period  of  time. 

Hirudo  may  be  a  descendant  of  the  land  leeches,  like 
Haemadipsa  ceylonica.  The  fact  that  its  eggs  are  laid  in 
earth  above  water-mark  would  indicate  such  a  descent. 

This  is  probably  the  case  with  another  fresh-water 
leech,  Clepsine  (No.  764  ;  PI.  765,  fig.  i),  which  is  a  fish 
parasite.1  Although  the  eggs  of  this  leech  are  not  laid  in 
cocoons,  yet  they  are  covered  after  attachment  to  some 
water  plant,  with  a  fluid  that  soon  hardens  and  which 
serves  for  protection.  The  parent  covers  the  eggs  with 
her  body  and  also  carries  the  young  about  with  her2  until 
they  are  old  enough  to  care  for  themselves.  The  devel- 
opment illustrates,  according  to  Whitman, 3  ontogenetic 
concentration  in  which  the  earlier  phases  of  one  stage 
appear  before  the  later  phases  of  the  preceding  stage  are 
completed.  It  is  in  a  worm  with  this  accelerated  develop- 
ment that  we  find  the  segments  of  the  body  distinct  in 
the  young  and  indistinct  in  the  adult.  PI.  765,  fig.  i,  is 
a  drawing  of  Clepsine  when  seven  days  old  and  when  it 
has  nearly  attained  the  form  of  the  adult.  The  internal 
organs  of  a  species  of  Clepsine  (C.  compJanata]  are  well 
shown  in  fig.  2,  which  is  a  dissection  that  has  been  treated 
with  reagents.  The  portions  colored  pink  and  blue  con- 
stitute the  sacculated  digestive  system  which  begins  at  the 
mouth  and  ends  in  the  rectum  (see  figs,  i,  2).  The  dark 
red  organs  are  the  excretory  organs  or  nephridia  which 
are  in  pairs  (fig.  2). 


1  Whitman,  Quart.  Journ.  Micr.  Sci.,  XVIII,  1878,  p.  224. 

2  Whitman,  loc.  dt,,  p.  225. 

3  Loc.  cit.,  p.  272. 


METAZOA VERMES.  309 

There  is  a  marine  leech,  Pontobdella  muricata  Linn. 
(No.  766,  No.  767,  model)  which  not  only  attaches  itself 
to  another  animal,  the  skate,  but  even  fastens  its  eggs  to 
the  fish,  showing  that  the  parasitic  habit  has  become 
stronger  in  this  leech  than  in  Hirudo  which  lays  its  eggs 
in  earth,  or  in  Clepsine  which  deposits  its  eggs  in  water. 

The  indistinct  segments  of  the  body  of  the  adult  Pon- 
tobdella are  covered  with  warts,  but  a  short  distance  from 
the  head  a  few  segments  are  comparatively  smooth. 
There  is  a  large  anterior  sucker,  provided  with  papillae 
round  its  edge  by  means  of  which  the  animal  becomes 
attached. 

The  Hirudinia  have  much  in  common  with  the  Oli- 
gochaeta,  as  already  stated,  but  their  semiparasitic  habits 
and  consequent  change  of  environment  have  brought 
about  peculiar  modifications  of  structure.  Having  given 
up  very  largely  the  swimming  mode  of  locomotion,  the 
parapodia  have  disappeared  and  some  of  the  segments  of 
the  body  have  become  modified  into  an  anterior  and  a 
posterior  sucker  which  are  used  chiefly  for  the  purposes 
of  attachment,  though  they  are  also  efficient  organs  in 
creeping. 

GEPH\REA. 

The  trochophore  of  the  Gephyrean  Echiurus  (PI.  768, 
fig.  T),  has  all  the  typical  characters  of  the  trochophore 
of  the  Chaetopods,  and  it  is  also  similar  to  the  trocho- 
phore of  Mollusca.  The  larva  (fig.  2)  is  segmented  in  the 
posterior  part  of  the  body,  but  early  in  the  development 
the  segments  disappear  (fig.  3,  side  view  of  an  older  stage 
than  fig.  2)  and  no  trace  of  them  is  seen  in  the  young 
Echiurus  (fig.  4)  which  is  essentially  like  the  adult. 

In  this  genus  the  mouth  is  at  the  anterior  end  and  the 
anus  is  terminal  as  in  the  Chaetopods.  There  are  no 
parapodia,  but  ventral  setae  occur,  and  two  circles  of 
bristles  at  the  posterior  extremity.  Besides  these  organs 


310  SYNOPTIC    COLLECTION. 

there  are  also  regular  rows  of  papillae  encircling  the  body 
(figs.  3,  4). 

It  is  interesting  to  note  that  the  larva  of  another 
Gephyrean,  Phascolosoma  vulgar e  Dies.  (No.  769,  model) , 
possesses  setae  which  are  lost  before  the  animal  attains 
adult  size.  This  is  probably  owing  to  the  habit  of  the 
worm  of  living  in  a  shell,  usually  a  univalve,  that  it  has 
found  on  the  beach.  The  opening  being  too  large,  the 
animal  builds  out  a  long  tube  composed  of  mud  and  sand 
cemented  together  by  a  secretion  of  its  body.  The  large 
plump  body  stays  within  the  shell,  while  the  long  pro- 
boscis is  put  out  of  the  tube. 

The  development  of  Sipunculus  is  remarkably  abbre- 
viated (Hatschek).  Even  the  larva  shows  no  trace  of 
segments,  such  as  we  have  seen  in  the  larva  of  Echiurus. 

This  genus  differs  from  the  majority  of  worms  by  hav- 
ing distinct  longitudinal  ridges  extending  from  one  end  of 
the  body  to  the  other.  The  shape  of  the  body  is 
peculiar.  The  extreme  forward  end  from  which  the  pro- 
boscis extends  (No.  770,  Sipunculus  tessellatus}  is  small  as 
compared  with  the  rest  of  the  anterior  region,  which  is 
greatly  swollen.  Near  the  middle,  the  body  decreases  in 
size  only  to  swell  out  at  the  posterior  end.  The  mouth 
is  surrounded  by  tentacles,  and  the  anus  is  situated  on 
the  dorsal  side  of  the  anterior  region. 

The  preparation  (No.  771)  shows  the  long  alimentary 
canal  which  in  the  animal  coils  and  bends  upon  itself  and 
ends  in  the  anterior  region  as  already  stated.  The  four 
large  retractor  muscles  of  the  oral  sac  and  their  points  of 
attachment  to  the  wall  of  the  body  are  also  clearly  seen. 

Besides  these  muscles,  Sipunculus  is  unusually  well 
supplied  with  locomotor  muscles,  having  three  sets,  cir- 
cular, oblique,  and  longitudinal. 

The  nerve  cord  is  visible  in  the  preparation  (No.  771) 
as  a  white  thread  extending  from  one  end  of  the  body  to 
the  other. 

One  species  of  this  genus,  S.  nudus  (No.  772)  is  pro- 


METAZOA VERMES.  311 

vided  with  an  embryonic  membrane,  the  amnion,  when 
passing  through  its  development,  which  is  evidence  of 
acceleration  in  development.  The  shape  of  the  body  of 
the  adult  Sipunculus  nudus  is  more  nearly  equal  through- 
out than  in  S.  tessellatus.  The  tentacles  are  clearly  seen 
in  the  specimen  (No.  772),  and  also  the  anus  near  the 
anterior  end. 

NEMATODES. 

Free-living  Nematodes  are  extremely  abundant  in  the 
sand  of  beaches  and  of  rivers.  One  from  the  Mediter- 
ranean is  represented  by  Tricoma  cincta  (PI.  773,  figs,  i, 
2,  greatly  enlarged).  While  it  is  true  that  most  Nema- 
todes are  without  segments  or  appendages,  yet  there  is, 
according  to  N.  A.  Cobb,1  a  repetition  of  the  order  of 
arrangement  of  certain  organs,  both  external  and  internal. 
This  observer  mapped  the  position  of  all  the  hairs  on  the 
anterior  half  of  several  specimens  of  a  species  of  Spilo- 
phora.  A  comparison  of  the  results  showed  that  the  hairs 
were  arranged  in  almost  exactly  the  same  order  in  each 
case,  and  that  there  was  a  faint  trace  of  repetition  of 
arrangement  such  as  is  commonly  observed  in  segmented 
worms.  Tricoma  cincta  (PI.  773,  A,  the  head;  B,  the 
posterior  end  of  the  body)  shows  external  "  annulation  " 
which  is  certainly  similar  to  segmentation,  though  this 
does  not  extend  to  the  internal  organs.  The  body  cavity 
of  the  Nematodes  is  hollow  and  similar  to  that  of  Annelida 
generally. 

Besides  the  free-moving  species  there  is  a  great  num- 
ber of  parasites.  Many  of  these  spend  their  early  larval 
life  in  water  and  afterwards  become  parasitic  for  a  shorter 
or  longer  time  as  the  case  may  be. 

1  Parasites  of  Stock,  New  South  Wales  Dept.  Agric.,  Misc.  Publi- 
cation 215,  1898,  p.  18. 


312  ' 


SYNOPTIC    COLLECTION. 


The  class  illustrates  great  variation  in  the  process  of 
development,  not  less  than  fourteen  different  modes  hav- 
ing been  described  by  von  Lin  stow.  Accompanying  this 
widespread  variation  there  is  a  marked  development  of 
adaptive  characters,  the  cause  lying  in  the  fact  that  the 
Nematodes  "display  a  variation  in  the  conditions  under 
which  they  live  greater  than  that  of  any  other  group  of 
Helminths.''* x  For  these  reasons  they  are  placed  among 
the  more  specialized  of  the  subkingdom  of  Vermes, 
although  not  at  the  extreme  end  of  the  genealogical 
record,  since  their  structure  is  not  profoundly  modified 
and  the  adults  have  «ot  departed  so  far  from  their  young 
as  those  of  the  Acanthocephala,  Trematodes,  or  Cestodes, 
to  be  described  farther  on. 

It  would  seem,  indeed,  as  though  the  parasitic  habit 
had  not  been  long  acquired  by  the  members  of  this  class, 
and  that  therefore  the  effects  of  this  habit  had  not  become 
fixed  in  the  organization  to  such  a  degree  as  to  cause  its 
complete  modification. 

The  hair  worm,  Gordius  (PI.  774;  No.  775,  9),  lays 
its  eggs  in  water  where  a  portion  of  the  first  larval  life  is 
spent. 

The  embryo  of  Gordius  subbifurcus  while  still  within 
the  egg  (PI.  774,  fig.  i)  has  the  body  divided  into  two 
regions,  both  of  which  are  segmented  (clearly  seen  in  fig. 
3).  At  the  anterior  end  the  proboscis  forms;  this  is 
retracted  in  fig.  2  but  is  thrown  out  in  fig.  3  ;  the  latter 
figure  shows  also  the  well  developed  head.  In  this  con- 
dition the  embryo  escapes  from  the  egg  and  swims  freely 
about. 

Some  members  of  the  family  to  which  Gordius  belongs 
have  two  larval  stages.  The  first  is  segmented  and  has 
the  body  divided  into  a  distinct  head,  middle,  and  poste- 
rior region  ;  but  the  second  stage,  though  still  segmented, 
is  without  a  head.  These  immature  stages  are  mostly 

1  Leuckart,  Parasites  of  Man  (translation),  1886,  p.  53. 


METAZOA VERMES.  313 

passed  in  the  body  cavities  of  insects ;  afterward  Gordius 
becomes  free  in  water,  where  it  sexually  matures.  The 
body  of  the  adult  (No.  775,  Gordius  varius  taken  from  a 
well)  shows  no  vestiges  of  segmentation  nor  of  distinct 
regions. 

Ascaris  (  =  Angiostomum)  (No.  776)  is  one  of  the 
parasites  of  man,  being  found  usually  in  the  small  intes- 
tine. The  eggs  pass  from  the  intestine  and  develop  in 
water  or  moist  earth,  and  the  larval  life  is  spent  in  this 
environment.  It  is  not  known  how  the  larva  reaches  its 
place  of  final  development.  The  adult  has  lost  its  seg- 
mented structure,  also  its  locomotor  and  external  respir- 
atory organs.  The  body  is  more  or  less  cylindrical  and 
tapers  at  both  ends,  the  head  not  being  differentiated. 
The  digestive  system  is  present  with  the  mouth  in  front 
and  the  anus  at  the  posterior  end.  In  this  condition  the 
animal  is  an  hermaphrodite.  No.  777  is  a  preparation  of 
a  female  Ascaris  (A.  lumbricoides)  showing  the  intestine 
and  generative  organs.  The  female  is  ten  to  fourteen 
inches  long,  while  the  male  is  only  from  four  to  six  inches 
in  length. 

Another  Nematode  worm,  Filaria  epinocaudata  (No. 
778)  is  parasitic  in  the  seal,  those  of  No.  778  being  found 
in  the  right  ventricle  and  at  the  base  of  the  pulmonary 
artery  of  Phoca  vitulina.  The  thread-like  body  is  with- 
out segmentation,  distinct  head,  branchiae,  or  locomotor 
organs.  Filaria  insignis  (No.  779)  was  taken  from  the 
foot  of  a  raccoon. 

The  guinea-worm  of  hot  climates,  Filaria  medinensis, 
passes  its  earliest  stages  in  the  water,  but  its  later  larval 
life  is  spent  in  the  little  crustacean,  Cyclops.  The  latter, 
in  drinking  water,  is  swallowed  by  man.  The  parasite 
then  finds  its  way  to  the  outer  integument  of  its  host, 
where  just  under  the  skin  of  the  leg  or  the  shoulder  it 
becomes  encysted.  In  time  it  matures  sexually  and  pro- 
duces living  young  which  bore  through  the  skin  and  find 
their  way  to  the  water. 


314  SYNOPTIC    COLLECTION. 


ACANTHOCEPHALA. 

The  development  of  Echinorhynchus  (No.  780),  a 
member  of  the  Acanthocephala,  is  instructive  as  showing 
what  changes  a  parasitic  mode  of  life  may  bring  about  in 
the  embryo.  The  egg,  in  cleaving,  forms  four  protective 
embryonal  membranes.  At  a  very  early  stage  the  embryo 
develops  a  disc  with  hooks,  and  the  anterior  end  of  the 
body  on  which  they  are  situated  can  be  retracted.  In 
this  condition  the  embryo  still  enclosed  in  its  envelopes 
leaves  the  parent  while  in  the  intestine  of  the  hog  (£. 
gigas)  or  the  fish  (£.  angustatus)  and  from  the  intestine 
is  ejected  with  the  faeces.  The  embryos  of  E.  gtgas  are 
swallowed  by  the  larvae  of  Cetonia  aurata  while  eating. 
In  the  stomach  of  this  beetle  the  envelopes  soften  and 
the  enclosed  embryo  becomes  free.  It  now  pierces  the 
intestine  of  this  intermediate  host  and  undergoes  a  most 
complicated  change  of  structure  resulting  in  a  stage  simi- 
lar to  the  adult.  This  adult,  however,  does  not  become 
sexually  mature  until  its  intermediate  host,  the  beetle,  is 
devoured  by  its  permanent  host,  the  hog :  in  the  intestine 
of  the  latter  animal  its  final  development  is  reached. 

This  worm  is  an  excellent  example  of  specialization  by 
the  suppression  of  parts.  The  process  has  gone  so  far 
that  not  only  is  the  adult  worm  without  a  mouth  and  ali- 
mentary canal,  but  the  digestive  tract  is  not  even  indi- 
cated in  the  embryonic  development.  This  tends  to 
prove  that  the  ancestors  of  Echinorhynchus,  near  and 
remote,  have  led  an  endoparasitic  life,  living  upon  a  sup- 
ply of  already  digested  food  which  has  been  absorbed  by 
the  walls  of  the  body. 

Another  change  has  taken  place  in  these  worms, 
whereby  the  ventral  side  of  the  body  cannot  be  distin- 
guished from  the  dorsal  side,  —  a  most  unusual  modifica- 
tion of  structure. 

The   Annelida   (consisting  of   the  Chaetopoda,  Oligo- 


METAZOA VERMES.  315 

chaeta,  and  Hirudinia),  the  Gephyrea,  Nematodes,  and 
Acanthocephala,  may  be  considered  as  one  division  of 
worms  in  which  the  Chaetopods  are  the  most  primitive, 
though  at  the  same  time  they  are  examples  of  specializa- 
tion by  addition,  while  the  Nematodes  and  Acantho- 
cephala through  the  habit  of  parasitism  are  the  most 
modified,  and  offer  good  illustrations  of  specialization  by 
reduction. 

The  next  division,  including  the  Nemertea,  Turbellaria, 
Trematodes,  and  Cestodes,  consists  of  secondary  forms 
which  illustrate  in  a  marked  degree  acceleration  in  devel- 
opment and  extreme  specialization  by  the  suppression  of 
parts. 

NEMERTEA. 

The  Pilidium  larva  (PI.  781,  Linens  lacteus}  peculiar 
to  some  Nemertines,  has  an  incomplete  digestive  system 
and  when  older  its  structure  is  complicated  by  having 
the  young  worm  enclosed  within  (PL  782,  Pilidium 
gyrans),  the  development  of  which  is  abbreviated.1 

Most  Nemerteans  enclose  their  eggs  in  cocoons  and 
the  embryo  is  sometimes  protected  by  a  membrane,  the 
amnion.  There  are  various  modes  of  development,  but 
the  majority  are  without  a  metamorphosis,  the  develop- 
ment indicating  a  concentration  of  stages.  Some  are 
even  viviparous,  and  this  process  is  usually  the  result  of 
acceleration  in  development. 

Most  Nemerteans  are  unsegmented  though  there  are 
some  species  that  show  traces  of  segmentation  (Balfour), 
and  the  segmented  condition  is  indicated  in  various  sys- 
tems of  organs.2 

While  the  young  are  usually  free-swimming,  the  adults 
are  generally  found  under  stones  on  the  shore.  These 

1  Balfour,  Comp.  Embryol.,  I,  1880,  p.  169. 

2  Gegenbaur,  E!em.  Comp.  Anat.,  1878,  p.  130. 


316  SYNOPTIC    COLLECTION. 

characters  indicate  secondary  and  not  primary  condi- 
tions. 

The  group  is  represented  in  the  Synoptic  Collection  by 
Cerebratulus,  Meckelia,  and  Borlasia. 

Cerebratulus  marginatus  (No.  783) ,  has  an  extremely 
long  body  which  is  indistinctly  segmented.  The  forward 
end  is  small  and  a  long  slender  organ,  the  proboscis, 
which  is  characteristic  of  the  Nemertines,  extends  from 
it  (PI.  784,  C.  tristis  Hubr.).  The  figure  shows  that  this 
proboscis  is  not  thrown  out  of  the  mouth  but  has  a  sep- 
arate opening  above  the  mouth.  It  is  provided  with  a 
sheath  and  sharp  spines  and  is  thought  to  be  an  organ  of 
defence.  The  head  also  possesses  deep  lateral  slits  or 
olfactory  organs. 

There  are  no  locomotive  organs  on  the  sides  of  the 
body.  It  is  generally  stated  that  these  worms  move  by 
the  cilia  which  cover  the  whole  body,  but  according  to 
MTntosh,1  this  statement  is  incorrect.  This  author 
maintains  that  the  adhesion  of  the  body  to  the  mucus 
which  is  secreted  by  the  worm  gives  the  animal  sufficient 
purchase  for  the  use  of  its  facile  muscles,  so  that  it  is 
muscular  rather  than  ciliary  action  which  causes  locomo- 
tion. Many  of  these  worms,  however,  lie  for  hours  in 
what  would  seem  to  be  a  torpid  state,  and  Cerebratulus, 
although  a  good  swimmer,  has  the  habit  of  frequenting 
empty  bivalve  shells  in  which  it  remains  quiescent. 

Meckelia  macrorrhochma  Scrim.  (No.  785,  model),  is 
large  in  the  anterior  region  but  is  without  a  distinct  head 
and  the  body  tapers  posteriorly.  It  is  without  external 
locomotive  or  respiratory  organs.  Like  Cerebratulus  it 
possesses  the  proboscis  enclosed  in  a  sheath  which  has  a 
distinct  opening  just  above  the  mouth. 

Other  Nemertean  worms  are  Borlasia  trilineata  Schm. 
(No.  786,  model),  and  Nemertes  flaccida  O.  F.  Mull.  (No. 

1  Monograph  on  Brit.  Annelids,  part  i,  1873,  p.  6.  (Ray 
Society.) 


M  ETAZOA VERMES.  317 

787).  Borlasia  unlike  Meckelia  tapers  at  both  ends, 
making  it  difficult  at  first  sight  to  tell  which  is  the  ante- 
rior region.  These  worms  possess  the  same  general 
characters  as  Cerebratulus,  though,  as  compared  with 
this  giant,  they  are  diminutive  members  of  their  class. 


TURBELLARIA. 

The  Nemertea  and  Turbellaria  have  been  considered 
by  many  naturalists  as  the  representatives  of  the  ances- 
tral forms  of  not  only  the  Platyhelminthes  or  group  of 
Flat  Worms,  but  of  the  whole  subkingdom  of  Vermes. 
The  reasons  why  they  are  here  regarded  as  derived  rather 
than  primitive  forms  are  the  following:  — 

First :  The  trochophore  stage  of  development  is  not 
found  in  the  Turbellaria  nor  in  other  Platyhelminthes. 
Now,  since  this  stage  occurs  in  the  early  development  of 
many  classes  of  animals  and  in  the  Annelida,  as  we  have 
already  seen,  we  consider  it  of  great  phylogenetic  impor- 
tance. 

Secondly:  The  Turbellaria  (excepting  the  Polyclads) 
are  either  fresh-water  or  terrestrial  animals,  and,  there- 
fore, show  in  their  structural  features  and  mode  of  devel- 
opment the  specializations  peculiar  to  animals  with  such 
a  habitat.  -The  rest  of  the  class  of  Platyhelminthes  are 
extremely  specialized  by  the  suppression  of  parts.  In 
fact,  this  class  offers  some  of  the  best  illustrations  of 
specialization  by  reduction  to  be  found  in  the  whole  ani- 
mal kingdom. 

Thirdly :  While  it  is  true  that  most  of  the  Turbellaria 
are  unsegmented  in  both  the  young  and  the  adult  condi- 
tion, nevertheless  there  are  members  of  the  class  which 
are  segmented  when  young  and  which  lose  this  feature  on 
approaching  maturity.  This  tends  to  prove  not  only  that 
the  Turbellaria  and  Platyhelminthes  belong  to  the  great 
group  of  animals  with  segmented  bodies,  but  also  that 


318  SYNOPTIC    COLLECTION. 

the  segmented  condition  is  characteristic  of  larval  stages 
and  consequently  of  ancestral  forms,  and  is  lost  through 
semiparasitic  and  parasitic  habits. 

Fourthly  :  The  Turbellaria  have  a  complicated  diges- 
tive system.  The  reproductive  organs  are  also  complex, 
as  shown  by  Gamble.1  The  embryo  is  retained  in  the 
uterus  and  the  young  resemble  very  early  the  adult. 

Fifthly  :  When  the  trochophore  larva  of  an  Annelid  is 
compared  with  the  Pilidium  larva  of  a  Nemertean  or 
with  Miiller's  larva  of  a  Turbellarian  (see  Pis.  727,  782, 
789),  the  Annelid  trochophore  is  the  more  primitive  so 
far  as  we  are  able  to  judge.  This  is,  as  we  have  seen,  a 
spherical  body  surrounded  by  bands  of  cilia  and  contain- 
ing a  digestive  system  with  a  mouth  and  an  anus.  This 
trochophore  passes  into  the  worm  by  changes  which  are 
comparatively  simple  and  easily  followed.  The  Pilidium, 
on  the  other  hand,  has  a  bell-shaped  part  from  which 
hang  two  lobes.  The  mouth  opens  between  the  lobes 
and  the  anus  ends  blindly.  Within  this  organism  the 
worm  is  formed  by  complex  changes,  after  which  it  leaves 
the  Pilidium  and  the  latter  continues  to  live  some  time.'2 

Miiller's  larva,  as  will  be  seen  (PI.  789),  is  elongated  in 
shape  and  is  provided  with  eight  finger-like  prolonga- 
tions. Numerous  changes  are  undergone  before  this 
larva  assumes  the  adult  form  (see  p.  319). 

Sixthly  :  Most  Chaetopods  pass  through  a  trochophore 
stage  while  only  a  comparatively  small  number  of  Tur- 
bellaria (the  Cotylea  and  a  few  Acotylea  of  the  Polyclads) 
go  through  the  stage  represented  by  Miiller's  larva,  while 
the  rest  of  the  Polyclads,  the  Triclads,  and  the  Rhabdo- 
coela  have  either  a  modified  Miiller's  larva  or  are  without 
this  larval  form,  the  stage  being  skipped  altogether 
through  acceleration  in  development.  The  remaining 
classes  of  the  Platyhelminthes  (Trematodes,  Cestodes") 

1  Quart.  Journ.  Micr.  ScL  XXXIV,  1893,  p.  438. 

2  Balfour,  Comp.  Embryol.,  I,  1880,  p.  167. 


METAZOA VERMES.  319 

are  remarkable  for  complicated  processes  of  development 
which  illustrate  in  the  majority  of  cases  great  abbrevia- 
tion in  the  life  history. 

The  marine  Turbellaria  or  Polyclads  are  mostly  littoral 
animals,  but  a  few  genera  are  pelagic. 

Alaurina  composita  Metsch.  (PI.  788),  was  found  at  the 
surface  of  the  sea.  Its  body  is  segmented  *  and  is  long, 
narrow,  and  covered  with  cilia.  It  has  a  tactile  organ, 
the  proboscis,  at  the  anterior  end.  There  are  stiff  hairs 
at  the  posterior  end,  and  sometimes  paired  setae  occur  on 
the  sides.2 

The  life  history  of  those  Turbellaria  which  pass 
through  a  metamorphosis  begins  (after  the  embryo  is 
free  from  the  egg)  with  the  stage  known  as  Miiller's  larva 
(PI.  789,  fig.  i,  dorsal  view;  fig.  2,  ventral  view;  prob- 
ably figures  of  the  genus  Thysanozoon  s).  The  body  is 
somewhat  elongated  and  possesses  eight  finger-like  lobes 
around  which  extends  a  band  of  cilia.  Three  of  these 
lobes  are  dorsal  (fig.  i,  the  posterior  pair  of  lobes  and 
the  single  median  lobe  just  back  of  the  eyes),  two  lateral 
(fig.  i,  the  anterior  pair),  and  three  ventral  (fig.  2,  a  short 
pair  and  a  single  one  just  back  of  the  eyes).  The  mouth 
is  in  the  center  of  these  three  lobes,  and  can  be  seen  in 
fig.  2  and  also  through  the  body  in  fig.  i.  When  this 
swimming  larva  changes  into  the  creeping  adult,  the  lobes 
grow  smaller  till  they  disappear  altogether,  the  ciliated 
band  is  absorbed,  and  the  form  becomes  flattened. 

The  more  complete  development  of  a  Turbellarian  is 
shown  in  PL  790,  figs,  i-io  which  represent  Yungia 
aurantiaca  (figs,  i— 8)  and  Thysanozoon  brocchi  (figs.  9, 

1  Metschnikoff,  Ann.   and   Mag.  Nat.  Hist.,  (3)  XVIII,  1866,  p. 
61  ;  Huxley,  in   his   Invertebrata,  1897, .p.  157,   says,    "None   are 
divided  into  distinct  segments   except  the  genus  Alaurina,  in  which 
there  are  four." 

2  Quart.  Journ.  Micr.  ScL  XXXIV,  1893,  p.  449. 

3  Korschelt  and  Heider,  Text-book  of  the  Embryology  of  Inverte- 
brates, part  i,  1895,  p.  1 66. 


320  SYNOPTIC    COLLECTION.    • 

10).  The  very  young  larva  (fig.  i,  dorsal  view;  fig.  2, 
ventral  view)  is  provided  with  eye-spots  and  ciliated  lobes. 
The  body  and  lobes  increase  in  size,  and  the  larva  (fig.  3, 
dorsal  view;  fig.  4,  ventral  view)  is  found  swimming 
freely  at  the  surface  of  the  sea.  The  body  elongates  (fig. 
5,  dorsal,  and  fig.  6,  ventral  view),  and  the  lobes  begin 
to  be  resorbed  (fig.  7,  dorsal,  and  fig.  8,  ventral  view). 
Finally  by  the  suppression  of  the  lobes,  the  young  sexual 
form  (fig.  9,  dorsal,  and  fig.  10,  ventral  view)  resulting 
from  the  metamorphosis  is  produced.  This  form  is 
essentially  like  that  of  the  adult. 

The  broad,  flat,  marine  Leptoplana  gigas  Schm.  (No. 
791,  model),  has,  like  Thysanozoon  and  most  of  its  group, 
an  unsegmented  body  with  the  mouth  near  the  center  of 
the  ventral  side.  The  digestive  system  is  extremely  com- 
plicated, as  shown  by  PL  792,  L.  alcinoi.  The  central 
stomach  gives  off  intestinal  branches  which  fill  the  body 
cavity  and  end  blindly,  there  being  no  anus.  These  ani- 
mals are  often  called  solid-bodied  worms  and  are  con- 
trasted with  the  hollow-bodied  forms,  such  as  the  Chaeto- 
pods,  Nematodes,  and  the  like. 

Among  the  Triclad  marine  Turbellaria,  Planaria  angu- 
lata  is  interesting  since  it  differs  from  most  of  its  class 
by  having  a  segmented  cylindrical  body  (PI.  793,  figs,  i, 
2)  which  in  the  course  of  development  loses  its  segments 
and  becomes  flattened. 

A  fresh-water  Triclad  Turbellarian,  Planaria  lactea 
Baer  (No.  794,  model),  is  a  flat  and  nearly  transparent 
worm.  Extending  down  the  back  is  the  digestive  system 
which  is  characteristic  of  the  Turbellaria,  as  we  have 
already  shown.  It  consists  in  this  genus  of  a  median 
tube  which  gives  off  two  branches.  Near  the  middle  of 
the  body  this  median  tube  divides  into  two  large  branches 
which  extend  backward  giving  off  smaller  branches.  At 
the  point  where  the  median  tube  divides  there  is  a  good- 
sized  bag,  the  proboscis,  which  seizes  the  food.  As  in 
the  Polyclads,  the  intestine  in  the  Triclads  ends  blindly, 
there  being  no  anus. 


METAZOA — VERMES.  321 

Although  many  naturalists,  as  we  have  said,  place  the 
Platyhelminthes  as  primitive  worms,  yet  at  the  same  time 
it  is  stated  that  even  the  Triclads  belonging  to  the  most 
generalized  division  of  this  group,  the  Turbellaria,  deposit 
their  ova  in  chitinous  cocoons  which  contain,  beside  the 
ova  proper,  large  numbers  of  amoeboid  cells  originating 
in  the  pouches  of  the  parent  and  serving  as  food  for  the 
young  embryo.  In  association  with  this  condition  of 
affairs  many  peculiarities  of  segmentation  and  growth 
occur  in  the  Triclad  embryos  all  of  which  must  be  con- 
sidered as  secondary  adaptations.1  These  facts  being 
true,  it  is  evident  that  the  Triclads  cannot  be  primitive 
worms. 

The  Turbellaria  include  not  only  marine  and  fresh- 
water forms  but  also  many  terrestrial  species. 


TREMATODES. 

The  Trematodes  are  built  upon  the  same  plan  of  struc- 
ture as  the  Turbellaria  but  this  plan  is  greatly  modi- 
fied by  parasitism.  All  the  group  excepting  the  Temno- 
cephala  are  either  external  or  internal  parasites,  and  there 
are  numerous  adaptive  characters  and  complicated  modes 
of  development.  A  good  illustration  of  the  Trematodes 
which  pass  through  a  metamorphosis  is  found  in  the 
fluke  worm,  Distomum  (  PI.  795  ;  No.  796,  a  specimen 
taken  from  the  liver  of  the  red  deer).  The  eggs  of  most 
flukes  pass  from  the  intestine  of  their  host  into  water, 
where,  as  in  the  case  of  Distomitm  hepaticum  (PI.  795, 
figs.  1-6) ,  they  become  ciliated  larvae  (fig.  i).  Very  soon 
this  larva  bores  into  the  body  cavity  of  a  snail  (Lim- 
naeus  minutus).  In  this  cavity  it  loses  its  cilia  and  be- 
comes a  sac-like  body  or  sporocyst  (fig.  2).  Its  germ 
cells,  seen  in  fig.  2,  grow  large  and  divide,  giving  rise  to 

1  McMurrich,  Invertebrate  Morphology,  1894,  p.  140. 


322  SYNOPTIC    COLLECTION. 

new  sporocysts  which  differ  from  the  original  sporocyst 
by  having  a  mouth  with  a  sucker  and  an  intestine,  but 
no  anus.  The  new  sporocysts  are  called  Rediae  or 
"parent-nurses"  (fig.  3).  The  wall  of  the  sporocyst 
breaks  and  the  Rediae  migrate  to  the  other  organs  of 
the  snail,  especially  the  liver,  and  there  develop  into 
Cercariae  (fig.  4)  which  are  provided  with  tails  (fig.  5,  a 
single  Cercaria  showing  the  anterior  and  ventral  sucker). 
In  this  stage  the  Cercaria  works  its  way  through  the  tis- 
sues of  its  host  and  seeks  the  water,  where,  however,  it 
stays  only  a  brief  time.  It  fastens  itself  to  the  plants  on 
the  shores  of  the  pond  and  becomes  encysted.  In  this 
state  it  is  swallowed  by  sheep  ;  in  the  stomach  of  this 
animal  the  cyst  is  dissolved  and  the  freed  worm,  finding 
its  way  to  the  liver  ^fig.  6,  a  young  fluke  in  which  the 
intestine  has  begun  to  branch),  develops  into  the  sexu- 
ally mature  Distomum  hepaticum  (fig.  7).  The  eggs  find 
their  way  through  the  bile  duct  to  the  intestine  and 
escape. 

One  of  the  most  remarkable  instances  of  acceleration 
in  development  is  found  in  Gyrodactylus  elegans  (PI.  797). 
Not  only  do  the  eggs  of  this  worm  develop  into  sexually 
mature  embryos  while  within  the  body  of  the  parent,  but 
the  embryos  thus  formed  also  develop  embryos  which  in 
turn  produce  eggs  in  process  of  development,  so  that  four 
generations  are  represented  by  a  single  specimen. 

Certainly  no  better  example  of  acceleration  in  sexual 
maturity  need  be  offered  than  these  viviparous  "  young," 
as  they  are  called,  containing  offspring  which  are  them- 
selves in  the  act  of  developing  eggs. 

The  figure  shows  the  adult  with  one  embryo  enclosed. 
The  esophageal  bulb  of  the  mother  and  embryo  are  seen  ; 
also  the  posterior  sucker  with  the  two  great  hooks. 


METAZOA VERMES.  323 


CESTODES. 

All  Cestodes  are  internal  parasites  and  illustrate  ex- 
treme specialization  by  a  profound  modification  of  some 
organs  and  by  the  total  suppression  of  others. 

The  important  fact  that  there  is  no  mouth  and  no 
digestive  system  in  either  the  young  or  the  adult  Cestode 
proves  how  far  removed  these  parasites  are  from  the 
primitive  ancestral  forms. 

The  tape-worm,  Taenia  solium,  found  in  the  intestine  of 
man,  is  an  instructive  example. 

Its  eggs  do  not  develop  in  water  nor  in  earth,  like  those 
of  the  tape-worm's  remote  ancestors,  but  within  the  body 
of  another  animal,  the  hog.  Thus  the  environment  has 
changed  throughout  the  whole  life'of  the  worm,  and  with 
this  complete  change  in  physical  surroundings  there  has 
followed  a  complete  change  in  structure.  The  eggs, 
which  may  be  seen  in  the  little  bottle  at  the  bottom  of 
the  jar  (No.  800),  leave  the  intestine  in  faecal  matter 
and  are  swallowed  by  swine  which  are  often  kept  in  un- 
clean places.  The  young  of  the  tape-worm  originally 
described  as  Cysticercus  cellulosae  Auct.  are  bladder-like 
and  for  this  reason  are  often  called  bladder-worms.  The 
figure  (PI.  798,  fig.  i)  shows  the  bladder  with  just  the 
beginning  of  the  head.  In  fig.  2  the  head  is  turned  in- 
ward, and  in  fig.  3  outward ;  between  the  head  and  blad- 
der the  neck  has  developed.  In  time  the  head  or  scolex 
of  this  larva  is  provided  with  hooks  and  suckers.  (No. 
799  is  the  young  of  another  species  of.  Taenia  which 
is  found  in  the  liver  of  the  rat.  These  are  swallowed 
by  the  cat  in  whose  intestine  they  develop.) 

The  larvae  of  Taenia  solium  bury  themselves  in  the 
flesh  of  the  hog,  which  is  often  eaten  by  man  in  a  raw  or 
half-cooked  condition.  In  this  new  situation  the  worm 
develops  rapidly.  The  bladder  is  cast  off.  The  head 
(PI.  798,  fig.  4)  has  a  double  circle  of  hooks  and  four 


324  SYNOPTIC    COLLECTION. 

suckers  (fig.  5)  for  the  purpose  of  attachment.  From 
the  neck,  which  is  smooth  in  front  and  irregularly  wrin- 
kled behind,  grow  out  sections  divided  by  regular  joints. 
This  process  continues  until  an  immense  number  have 
been  formed,  those  nearest  the  neck  always  being  the 
youngest  and  those  at  the  posterior  end  the  oldest. 

Weinland x  has  pointed  out  that  the  articulation  of  a 
Cestode  is  by  no  means  homologous  with  that  of  an 
earthworm  or  any  true  segmented  animal. 

When  we  consider  how  these  sections  develop  into  sex- 
ual organisms  or  proglottids  (fig.  6),  how  these  break 
away  from  the  chain  and  live  for  a  while  as  independent 
individuals  (Van  Beneden),  we  see  how  very  far  removed 
they  are  from  the  true  segments  of  the  typical  worm. 
They  serve  the  one  function  of  reproduction,  containing 
such  an  incredible  number  of  eggs  that  it  may  be  said 
"in  no  group  of  the  animal  kingdom  do  we  find  any 
fecundity  to  be  compared  to  this  of  a  cestode  worm."  2 

A  specimen  of  Taenia  now  in  the  possession  of  the 
Boston  Society  of  Natural  History  measures  thirty  feet, 
but  this  is  incomplete,  not  having  the  head  ;  while  the 
complete  specimen,  No.  800,  measures  sixteen  and  a  half 
feet.  The  tiny,  knob-like,  and  reddish  brown  head  is 
seen  on  the  right  of  No.  800,  a  short  distance  from  the 
bottom  of  the  jar.  The  youngest  sections  are  small  and 
narrow,  but  the  oldest  are  large  and  sexually  mature. 
Not  only  is  the  adult  without  a  mouth  and  digestive 
system,  —  the  fluid  being  absorbed  through  the  body 
wall, — but  no  nervous  system  has  been  discovered. 

1  Tape-worms  of  Man,  1858,  p.  9. 

a  Van  Beneden,  Animal  Parasites  and  Messmates,  1876,  p.  208. 


METAZOA  —  CRUSTACEA.  325 


CRUSTACEA. 


Section  12  (in  part),  Section  13,  and  Section  14 
fin  nart"L 


(in  part) 
ENTOMOSTRACA. 


The  Worms  with  the  remaining  large  classes  of  Inverte- 
brates—  the  Crustacea,  Arachnozoa,  Myriopoda,  and 
Insecta  — were  formerly  grouped  together  under  the  name 
of  the  Articulata  or  animals  with  articulated  bodies. 
Afterwards  the  Worms  were  placed  in  the  subkingdom  of 
Vermes,  and  the  other  classes,  taken  collectively,  were 
known  as  the  Arthropoda  or  animals  with  jointed  legs. 
Of  late  years  there  has  been  much  discussion  on  the 
question,  "  Do  the  Arthropoda  constitute  a  natural  group  ?" 
That  is,  have  these  different  classes  descended  from  a 
common  ancestor  ?  The  tendency  is  toward  a  negative 
answer,  and  the  giving  up  of  the  name  Arthropoda,  while 
the  classes  are  considered  separately,  each  having  its  own 
ancestral  forms.  This  course  we  have  followed  in  the 
Guide. 

The  trilobites  of  Cambrian  times  may  be  ancestral 
forms  of  the  Crustacea.  They  are  certainly  a  generalized 
group,  possessing  characters  in  common  not  only  with  the 
Crustacea  but  also  with  the  Arachnozoa.  This  being  the 
case,  it  may  be  that  some  pre-Cambrian  trunk  form  gave 
rise  to  both  groups  which  developed  and  spread  out 
into  separate  branches  reaching  down  to  the  present  day, 
while  the  parent  group  —  the  Trilobita  —  became  extinct 
in  Palaeozoic  times.1 

The  relationships,  however,  between  the  trilobites  and 

'See  Woodward,  Quart.  Journ.  Geol.  Soc.  London,  LI,  1895, 
p.  Ixxi. 


326  SYNOPTIC    COLLECTION. 

Limulus  of  the  Arachnozoa  are  so  natural,  and  the  bonds 
uniting  Limulus  with  the  scorpion  and  spiders  so  close, 
that  we  have  placed  the  trilobites  as  the  primitive  Arach- 
nozoa instead  of  the  primitive  Crustacea. 

Among  the  generalized  living  Crustacea  are  the  marine 
pelagic  Copepods  which  may  be  taken  to  represent  the 
ancestral  form  of  the  group.  These  exist  in  inconceivable 
numbers  both  in  the  tropical  waters  and  the  arctic  seas. 
Calanus  (=  Cetochilus)  (PI.  80 1,  figs.  1-3,  C.  septentri- 
onalis  Goodsir;  PI.  802,  figs,  i,  2,  C.  propinqnus  Brady), 
begins  life  with  few  parts  and  organs,  and  the  changes 
which  convert  the  larva  into  the  adult  are  of  the  simplest 
(Kingsley).  The  larva,  called  the  nauplius  (PI.  80 1,  fig.  i), 
has  a  body  consisting  of  one  part,  the  cephalothorax, 
which  is  provided  with  a  median  simple  eye  and  three 
pairs  of  appendages  corresponding  to  the  two  pairs  of 
antennae  and  one  pair  of  mandibles.  The  abdomen  grows 
out  (fig.  2)  and  more  appendages  are  developed  (fig.  3). 
This  continues  until,  after  several  moults,  the  adult  form 
is  attained. 

The  body  of  the  adult  Calanus  (PI.  802,  fig.  i,  dorsal 
view  of  female  ;  fig.  2,  side  view  of  the  same),  which  is 
less  than  a  quarter  of  an  inch  in  length,  is  made  up  of 
segments  most  of  which  are  distinct  and  freely  movable. 
The  cephalothorax  is  not  covered  by  a  carapace,  peculiar 
to  more  specialized  forms,  though  the  anterior  segments 
are  more  or  less  fused  together.  The  abdomen  is  pro- 
vided with  terminal  appendages  only,  but  the  cephalothorax 
has  two  pairs  of  antennae,  four  pairs  of  mouth  parts,  and 
four  or  sometimes  five  pairs  of  swimming-feet. 

The  anterior  pair  of  antennae  are  long  (fig.  2),  equalling 
the  length  of  the  body,  and  are  adapted  for  a  purely  nata- 
tory life.  They  are  spread  out,  according  to  Brady1  "  at 
right  angles  to  the  body,  acting  like  the  wings  of  a  hover- 
ing bird  and  so  suspending  the  animal  at  almost  perfect 

iChall.  Rep.,  Zool.,  VIII,  1883,  p.  30. 


METAZOA CRUSTACEA.  327 

rest  in  the  water."  At  other  times  they  are  used  as  oars 
and  each  powerful  stroke  propels  the  animal  a  consider- 
able distance  through  the  water. 

The  second  or  posterior  pair  of  antennae  are  divided 
into  two  branches  and  supplied  with  long  hairs.  These 
are  also  adapted  for  swimming.  The  mouth  parts  con- 
sist of  a  pair  of  strong  mandibles,  one  pair  of  maxillae 
which  carry  long  branchial  filaments,  and  two  pairs  of 
well  developed  maxillipeds.  The  five  pairs  of  rowing 
feet  aid  the  antennae  in  locomotion,  and  thus  it  is  seen 
that  the  pelagic  Copepods  are  preeminently  swimmers. 

Besides  the  marine  forms  of  Copepoda  there  are  many 
related  fresh-water  species,  the  most  familiar  of  which  is 
Cyclops  (PL  803,  fig.  i,  C.  brasiliensis,  $  ;  fig.  2,  C. 
vitiensis,  9  ).  In  the  fresh-water  forms  the  first  pair  of 
antennae  are  much  shorter  than  in  Calanus,  and  conse- 
quently the  animals  are  not  such  good  swimmers.  The 
setae  of  the  second  pair  open  and  close  like  the  fingers  of 
a  hand,  so  that  by  means  of  these  organs  Cyclops  can 
attach  itself  to  objects.  In  the  middle  of  the  forward 
part  of  the  cephalothorax  there  is  an  eye  that  appears  to 
be  single  but  which  in  reality  is  double. 

The  fifth  pair  of  legs  exist  as  vestiges  and  usually  have 
but  one  joint. 

The  female  (fig.  2)  carries  the  two  sacs  of  eggs  about 
with  her  for  a  time,  and  the  young  are  hatched  as  nauplii. 

Nearly  every  group  of  Crustacea  has  its  parasites  illus- 
trating specialization  by  the  reduction  of  some  organs 
and  the  modification  of  others.  The  Copepoda  are  no 
exception  to  this  rule ;  indeed,  they  offer  some  modified 
forms  which  are  far  removed  from  their  primitive  ances- 
tors. Such  are  Chondracanthus  (No.  804 ;  PI.  805) 
which  lives  in  the  gill  chamber  of  a  fish  ;  Penella  (No. 
806)  and  Lernea  (No.  807). 

The  body  of  Chondracanthus  (No.  804;  PI.  805, 
C.  gibbosus,  side  view)  has  lost  its  distinct  segmentation, 
while  the  abdomen  exists  as  a  vestige  only.  The  eyes 


328  SYNOPTIC   COLLECTION. 

have  disappeared  and  the  appendages  are  for  the  most 
part  jointless  and  lobe-like.  The  antennae  are  tiny  and 
indistinctly  jointed  (Baird).  The  mouth  parts  are 
adapted  for  piercing  and  sucking,  instead  of  for  biting 
as  in  non-parasitic  Copepods. 

Another  parasitic  form  of  this  group  is  Penella  (No. 
806),  which  bores  into  the  body  of  a  fish  and  lives  partly 
imbedded  in  the  flesh.  Its  long,  tubular  body  is  indis- 
tinctly segmented.  At  the  anterior  end  there  are  several 
pairs  of  vestigial  appendages,  while  at  the  other  extremity 
a  large  number  of  thread-like  organs  extend  beyond  the 
end  of  the  abdomen  and  give  a  plume-like  aspect  to  this 
part  of  the  body. 

One  of  the  most  modified  Copepoda  is  Lernea  bran- 
chialis  Linn.  (No.  807  ;  PL  808,  figs,  i,  2,  drawings  of  the 
same),  found  on  the  gills  of  codfish.  Parasitism  has 
brought  about  such  complete  changes  in  this  species  that 
it  is  only  the  young  stage  (fig.  i)  which  enables  one  to 
place  it  among  the  Crustacea.  In  this  stage  it  is  seen  to 
have  a  cephalothoracic  region  with  a  pair  of  eyes  and 
three  pairs  of  jointed  appendages. 

The  body  of  the  adult  (No.  807  ;  PI.  808,  fig.  2)  has 
lost  all  trace  of  segmentation  and  is  an  S-shaped  sac  with 
two  long  egg  masses  hanging  from  it.  There  are  no  eyes 
and  no  jointed  appendages,  the  antennae  even  having  dis- 
appeared. The  mouth  parts  are  horny,  root-like  organs 
which  are  buried  in  the  flesh  of  the  fish,  and  the  fluid 
food  is  obtained  by  suction. 

Phyllopoda.  The  group  of  Phyllopoda  is  of  special 
interest  since  it  contains  two  genera,  the  brine  Artemia 
and  the  fresh-water  Branchipus,  which  have  been  trans- 
formed the  one  into  the  other,  by  changing  their  envi- 
ronment. 

Artemia  salina  M.  Edw.  lives  in  salt  lakes.  By  gradu- 
ally decreasing  the  density  of  the  salt  water  during  sev- 
eral generations,  it  has  been  converted  into  the  fresh- 
water genus  Branchipus.  By  increasing  the  density  of 


METAZOA  —  CRUSTACEA.  329 

the  water  in  which  Artemia  salina  M.  Edw.  was  living,  it 
was  transformed  into  another  species,  Artemia  muhl- 
hauseni  M.  Edw.  Again,  this  brine  was  diluted  and 
Artemia  muhlhauseni  was  changed  back  to  Artemia 
salina.1  In  this  way  it  has  been  proved  that  not  only 
one  species  can  be  converted  into  another  species,  but 
that  the  same  is  true  of  genera. 

Figures  of  the  two  animals  would  not  bring  out  these 
changes  since  they  take  place  in  the  details  of  structure 
(such  as  the  number  of  the  abdominal  segments  and  the 
bristles  and  knobs  of  the  terminal  abdominal  append- 
ages), but  they  are  clearly  represented  in  PI.  809,  figs. 
1-8.  The  long  terminal  segment  of  the  abdomen  of 
Artemia  salina  is  seen  in  fig.  i  ;  this  becomes  divided 
into  two  segments  (fig.  2),  as  in  the  abdomen  of  Branchi- 
pus.  Figs.  3-8  show  the  gradual  reduction  of  the  bristles 
of  Artemia  salina  (fig.  3)  to  the  knobs  of  Artemia  muhl- 
hauseni (fig.  8). 

The  American  species  of  Artemia  (A.  gracilis  Verrill) 
(PL  8 10,  fig.  i)  lives  in  Great  Salt  Lake,  and  the  New  Eng- 
land species  of  Branchipus  (B.  vernalis  Verrill)  (fig.  2),  is 
often  found  during  the  spring  and  autumn  in  ponds  that 
dry  up  in  the  summer  time.  They  are  graceful  little 
creatures  that  swim  on  their  backs  with  great  rapidity, 
their  light  colored  bodies  contrasting  prettily  with  their 
brightly  tinted  locomotor  organs  which  combine  the 
function  of  feet  and  gills. 

Apus  lucanus  Packard  (No.  811)  is  a  fresh-water  spe- 
cialized Phyllopod.  The  anterior  part  of  the  body  is 
covered  with  a  large  carapace  which,  however,  is  not 
soldered  to  the  thoracic  region.  When  this  carapace  is 
removed  the  segmented  body  is  exposed  beneath.  It 
consists  in  this  genus  of  not  less  than  sixty-nine  seg- 
ments. 

1  For  further  information  see  Zeitschr.  f.  wiss.  Zoo!.,  XXV, 
Suppl.;  1875;  also  I2th  Ann.  Rep.  U.  S.  Geol.  and  Geogr.  Surv., 
1878,  part  i,  pp.  466-5-14. 


330  SYNOPTIC    COLLECTION. 

Bernard1  maintains  that  this  large  number  of  segments 
is  one  of  many  proofs  that  the  Apodidae,  and  with  them 
all  the  Crustacea,  have  arisen  from  carnivorous  worms. 
He  takes  great  pains  to  bring  out  the  resemblances  of 
Apus  to  a  carnivorous  worm,  but  in  doing  this  he  is  deal- 
ing with  adults,  and  is  attempting  to  connect  the  mature 
forms  of  one  subkingdom  with  those  of  another. 

On  the  other  hand,  Packard 2  considers  the  excessive 
number  of  segments  in  Apus  and  the  irrelative  repetition 
of  abdominal  feet  as  signs  of  a  vegetative  repetition  of 
parts  in  a  type  which  has  culminated  and  is  subject  to 
decline  and  extinction.  He  finds  that  the  Phyllopods  as 
a  whole,  especially  the  Apodidae  and  Branchipodidae, 
are  a  comparatively  recent,  extremely  specialized  group 
which  was  developed  under  exceptional  biological  condi- 
tions in  salt  lakes  or  in  bodies  of  fresh  water.  He  also 
points  out  the  important  fact  that  although  fossils  of 
Phyllopods  are  found  in  the  Palaeozoic  rocks,  they  appear 
to  have  been  fresh-water  forms,  since  their  remains  occur 
in  fresh-water  strata. 3 

The  eyes  of  Apus  are  prominent.  Extending  from  the 
ventral  side  are  the  two  pairs  of  long,  slender  antennae. 
Back  of  these  are  the  mouth  parts  and  swimming-feet 
(No.  8n). 

One  of  the  modified  Phyllopod  crustaceans  is  Estheria 
californica  Pack.  (No.  812).  No  one  could  imagine  at 
first  sight  that  this  animal  was  in  any  way  related  to  a 
Gammarus,  lobster,  or  crab.  The  fleshy  organs  are  cov- 
ered by  a  bivalve  shell  (PL  813,  fig.  i,  enlarged;  the  line 
shows  true  length  of  shell)  which  is  provided  with  a 
hinge,  with  small  umbones  placed  near  the  anterior  end, 
and  with  what  appear  to  be  distinct  lines  of  growth. 


1  The  Apodidae,  1892,  p.  18  (Nature  series). 

2  I2th  Ann.  Rep.  U.  S.   Geol.  and  Geogr.  Surv.,  1878,  part  i, 
p.  418. 

3  Loc.  cit.,  p.  419. 


METAZOA  —  CRUSTACEA.  381 

Packard1  states  that  these  so  called  "lines  of  growth" 
are  superficial  like  the  tubercles  and  spines  on  other 
Crustacea,  and  that  therefore  they  are  probably  a  kind  of 
ornamentation.  The  shell  is  in  reality  a  modification  of 
the  carapace  which  bends  downward  and  encloses  the 
whole  body.  The  fleshy  animal  (fig.  2,  with  one  valve 
removed)  has  the  segmented  body  and  jointed  append- 
ages which  prove  that  it  does  not  belong  to  the  class  of 
Pelecypods.  The  thoracic  and  abdominal  segments  are 
similar  and  bear  twenty-two  pairs  of  feet.  Most  of  these 
are  alike  in  structure,  but  the  first  two  pairs  in  the  male 
are  provided  with  claspers.  The  head  segments  are 
soldered  together. 


CIRRIPEDIA. 

Barnacles  have  undergone  numerous  modifications 
which  have  carried  them  far  from  the  primitive  ances- 
tral form.  The  young^  however,  is  a  free-swimming  nau- 
plius  (PI.  814,  fig.  i)  similar  to  that  of  other  generalized 
Crustacea.  It  possesses  the  two  pairs  of  antennae  and 
the  mandibles  which  are  locomotor  organs  as  in  other 
members  of  its  class.  After  moulting  twice  it  appears  as 
seen  in  fig.  2.  It  now  has  a  segmented  abdomen  which 
serves  as  a  rudder  and  the  cephalothoracic  appendages 
are  larger.  In  the  still  older  larval  stage  (fig.  3,  side 
view),  when  the  barnacle  is  preparing  to  settle,  the  parts 
and  organs  which  are  useful  in  swimming  become  reduced 
in  size  or  are  dispensed  with  altogether.  Thus  the  abdo- 
men is  a  mere  vestige,  while  the  compound  eyes  and  one 
pair  of  antennae,  wholly  disappear.  The  cement  duct  in 
the  remaining  pair  of  antennae,  which  connects-with  the 
cement  gland  in  the  stalk,  pours  out  its  cement  whereby 
the  barnacle  is  fastened  by  the  anterior  part  of  its  head 
to  a  rock. 

1  Loc.  dt.y  p.  377. 


332  SYNOPTIC    COLLECTION. 

If  a  barnacle  belongs  to  the  pedunculated  Cirripedia 
like  Lepas  (No.  815),  the  stalk  or  peduncle  grows  long 
and  the  shell  forms  at  its  farther  end ;  if,  on  the  other 
hand,  it  is  one  of  the  sessile  Cirripedia,  like  Balanus 
(Nos.  816-818),  the  shell  is  fastened  directly  to  the  rock 
and  the  barnacle  looks  as  figured  in  PL  814,  fig.  4.  A 
slightly  older  stage  is  represented  in  fig.  5,  with  the  tho- 
racic appendages  extended. 

The  adult  Lepas  anatifera  Linn.  (No.  815)  is  provided 
with  a  long  contractile  stalk  by  which  it  is  usually  attached 
to  some  floating  object.  At  the  end  of  this  stalk  is  the 
shell  which  is  made  of  five  plates.  The  shell  protects 
the  viscera,  the  mouth  with  its  mandibles  and  two  pairs 
of  maxillae,  and  the  six  pairs  of  feathery  thoracic  legs 
which  have  become  transformed  into  organs  for  catching 
food.  It  was  the  discovery  of  these  jointed  appendages 
which  caused  the  barnacle  to  be  removed  from  the  Mol- 
lusca  and  placed  with  the  Crustacea. 

In  the  specimens  (No.  815),  as  in  the  undisturbed 
living  Lepas,  these  organs  are  seen  extending  from  the 
shell ;  when  the  animal  is  disturbed  they  are  withdrawn 
and  a  transverse  muscle  draws  the  valves  tightly  to- 
gether. 

The  segments  of  the  body  are  very  indistinct,  while, 
during  the  period  the  animal  was  becoming  adapted  to  a 
sedentary  life,  the  abdomen  became  a  mere  vestige  and 
its  appendages  disappeared. 

Lepas,  like  the  Cirripedia  generally,  has  no  heart  or 
specialized  circulatory  organs  and  probably  no  respiratory 
system. 

The  more  common  form  of  barnacle  is  sessile,  the  stalk 
not  being  developed.  In  the  specimen  (No.  816)  several 
of  these  barnacles  have  made  their  home  upon  one  valve 
of  Pecten.  The  opening  of  the  pyramidal  shell  of  the 
barnacle  is  closed  by  four  valves  ;  in  some  of  the  speci- 
mens, however,  these  valves  are  open  and  the  cirri  are 
extended.  These  delicate  organs  are  still  more  plainly 


METAZOA CRUSTACEA.  333 

seen  in  No.  817,  Balanus  hameri,  where  they  occur  so 
large  in  size  that  they  can  be  easily  studied. 

•Variation  in  the  color  and  ornamentation  of  the  shell 
is  well  shown  by  Balanus  t'mtinnabulum  Linn.  (No.  818). 
In  three  specimens  the  shell  is  smooth,  while  the  speci- 
men on  the  right  is  ridged. 

Sometimes  barnacles  attach  themselves  to  a  whale  and 
become  imbedded  in  its  skin.  This  is  the  case  with 
Coronula  diadema  Blainv.  (No.  819).  The  usual  conical 
shell  may  become  modified  into  a  tube,  as  in  Tubicinella 
balaenarum  (No.  820).  It  is  made  of  eight  vertical  sec- 
tions and  is  marked  by  circular  ridges  and  perpendicular 
striae.  At  the  top  the  four  valves  are  open  in  No.  820, 
as  when  the  thoracic  appendages  or  food-catchers  are  put 
out. 

The  barnacle  Concho derma  aurita  Olf.  (No.  821)  is  a 
peculiarly  modified  form.  The  young,  represented  by 
four  specimens  in  the  bottom  of  the  bottle,  have  a  short 
peduncle  and  a  body  that  is  similar  in  shape  to  that  of 
Lepas  (No.  815),  though  it  is  never  covered  by  a  shell. 
In  the  two  youngest  specimens  this  body  is  colorless,  but 
in  the  two  older  ones  it  is  distinctly  banded  with  brown. 
As  Conchoderma  grows  older  the  peduncle  becomes  long 
and  the  body  less  compressed,  while  both  are  dark  colored. 
From  the  upper  side  of  the  body  grow  out  two  tubular 
organs  which  are  very  conspicuous  in  the  adult  (No.  821). 
Their  function  is  not  known  with  certainty,  though  Kings- 
ley  thinks  they  may  be  respiratory  organs. 


MALACOSTRACA. 

An  ancestral  form  of  the  Malacostraca  may  be  repre- 
sented by  Palaeocaris  typus  M.  &  W.  (PI.  822,  fig.  i, 
enlarged  three  diameters) .  The  body  is  long  and  except- 
ing the  head,  is  made  up  of  distinct  and  similar  segments 
which  are  uncovered  by  a  carapace.  The  two  pairs  of 


334  .          SYNOPTIC    COLLECTION. 

antennae  are  largely  developed  and  these  were  probably 
used  as  locomotor  organs.  The  mouth  parts  are  not  pre- 
served, so  that  their  structure  is  not  known.  The  thoracic 
legs  extend  forward;  they  are  undivided  at  their  ends,  and 
the  anterior  pairs  are  apparently  not  differentiated  into 
organs  of  prehension  or  mastication,  but  all  are  useful  as 
swimming  organs.  Most  of  the  abdominal  segments  bear 
a  pair  of  appendages  which  are  simple  in  structure  (fig. 
2,  enlarged  four  times),  and  like  the  thoracic  appendages 
were  used  in  locomotion.  The  last  segment  or  telson 
carries  a  pair  of  swimmerets  (fig.  3 )  which  indicate  that 
this  portion  of  the  abdomen  is  a  true  segment,  and  which 
also  give  additional  proof  that  Palaeocaris  was  a  good 
swimmer. 

It  is  generally  conceded  that  the  Malacostraca  can  be 
traced  back  to  the  group  described  by  Packard  as  the 
Phyllocaridae,  the  only  living  representative  of  which  is 
Nebalia.  One  of  the  ancestors  of  Nebalia  is  probably 
Ceratiocaris  (PL  823,  C.  papilio  Salter),  in  which  a  cara- 
pace covers  the  thorax  and  a  part  of  the  abdomen.  The 
antennae  are  obscure  and  are  indicated  in  the  figure  by 
broken  lines.  The  anterior  projection  of  the  carapace  or 
the  rostrum  ( PI.  823)  has  separated  from  the  carapace. 
The  resemblance  of  Ceratiocaris  to  Nebalia  is  marked. 
The  latter  is  a  generalized  form  combining  Copepod,  Phyl- 
lopod,  and  Decapod  features.1  The  development  is  with- 
out a  metamorphosis  and  the  young  and  adult  resemble 
each  other.  Nebalia  bipes  Fabr.  (No.  824;  PI.  825,  figs. 
1-6,  Nebalia  geoffroyt)  is  a  marine  form  which  has  the 
segments  of  the  thorax  and  abdomen  similar  and  distinct, 
though  all  of  the  former  and  four  .of  the  latter  are  covered 
by  a  carapace  (fig.  i,  nearly  natural  size).  In  .fig.  2  one 
side  of  the  carapace  has  been  cut  away  exposing  the  body 
beneath.  The  eight  thoracic  segments  can  be  easily 
counted,  and  each  carries  a  pair  of  appendages  in  the 

1  Woodward,  Quart.  Journ.  Geol.  Soc.  London,  LI,  1895,  p. 
Ixxxiii. 


METAZOA  —  CRUSTACEA.  335 

form  of  leaf-like,  gill-bearing  thoracic  legs  (fig.  3).  The 
eight  abdominal  segments  are  also  distinct.  The  first 
four  of  these  carry  each  a  pair  of  swimmerets  consisting 
of  a  basal  stem  and  two  leaf-like  parts  (fig.  4) ;  the  fifth 
and  sixth  pairs  of  appendages  are  small,  and  the  last  two 
segments  are  without  swimmerets,  though  the  terminal 
segment  carries  a  pair  of  spines.  There  is  no  telson  in 
Nebalia,  and  in  this  respect  the  genus  differs  from  most 
Crustacea.1 

The  segments  of  the  head  are  consolidated,  but  as 
there  are  six  pairs  of  cephalic  appendages  it  is  inferred 
that  this  region  of  the  body  is  made  up  of  as  many  seg- 
ments. The  dorsal  and  lateral  portions  of  these  segments 
have  grown  backward  forming  the  carapace  which  not 
only  covers  the  thoracic  region  but  also  four  of  the  abdo- 
minal segments,  as  already  stated.  In  front,  a  movable 
plate,  called  the  rostrum,  is  hinged  to  the  carapace  which 
the  animal  can  move  up  and  down  at  pleasure.  The 
appendages  of  the  head  are  a  pair  of  eye-stalks  and  two 
pairs  of  well  developed  antennae  (fig.  2),  a  pair  of  mandi- 
bles (fig.  5),  and  two2  pairs  of  maxillae  (figs.  6,  7),  mak- 
ing six  pairs  attached  to  the  head. 

Stomatopoda.  The  young  of  Squilla,  first  described  as 
Alima  (PI.  826,  fig.  i,  Squilla  empusa  Say),  has  a  long, 
loosely  articulated  body.  The  posterior  thoracic  segments 
are  not  covered  by  the  carapace  and  these  segments  are 
without  appendages,  none  being  developed  after  the  large 
grasping  legs  which  correspond  with  the  second  pair  of 
maxillipeds.3  The  flat  abdomen  is  greatly  extended  and 
bears  a  few  pairs  of  swimmerets. 

1  According  to  Claas  (Ann.  and  Mag.  Nat.  Hist.,  (6),  III,  1889, 
p.  441)  the  last  two  segments  of  the  abdomen  represent  the  telson 
of  the  Malacostraca. 

2  Lang  says  one  pair,  making  five  pairs  to  the  head.      Packard 
describes  and  figures  six  pairs   (i2th  Ann.   Rep.   U.   S.  Geol.  and 
Geogr.  Surv.,  1878,  part  i).      Woodward  says  three  pairs  of  mouth- 
parts  (Quart.  Journ.  Geol.  Soc.  London,  LI,  1895,  p.  Ixxxiv). 

3  Faxon,  Mem.  Mus.  Comp.  Zool.,  IX,  no.  i,  1882,  explanation 
of  PI.  vii. 


336  SYNOPTIC    COLLECTION. 

All  the  appendages  of  this  Stomatopod  are  adaptive 
even  at  this  early  age,  and  Brooks  l  has  shown  that  dur- 
ing the  long  larval  life  the  larvae  have  undergone  many 
secondary  modifications  which  have  no  reference  to  the 
life  of  the  adult  and  are  therefore  unrepresented  in  the 
adult  organism.  Indeed,  the  larvae  differ  among  them- 
selves, says  this  investigator,  "more  than  the  adults,  thus 
reversing  the  general  rule  that  larvae  are  less  specialized 
and  exhibit  clearer  evidence  of  genetic  relationship  than 
mature  animals."  At  the  same  time  Brooks  has  shown 
that  the  changes  which  convert  the  larva  into  the  adult 
are  very  gradual,  and  that  the  development  may  be 
regarded  as  the  simplest  expression  of  the  extremely  com- 
plicated metamorphosis  of  the  specialized  Crustacea. 
Inasmuch  as  the  changes  are  slight  compared  with  those 
of  most  stalk-eyed  Crustacea,2  we  have  a  sufficient  reason 
for  placing  Squilla  among  the  more  generalized  Malacos- 
traca. 

When  fully  grown,  Squilla  (No.  827,  6".  nepa  Latr.) 
excavates  holes  in  the  sand,  and  one  species,  Lysiosquilla 
excavatrix,  buries  itself  with  the  exception  of  the  tips  of  its 
eye-stalks  while  waiting  for  its  prey.  The  body  of  Squilla, 
like  that  of  the  larva,  is  long  and  made  up  largely  of  dis- 
tinct and  movable  segments.  When  viewed  from  the 
dorsal  side  (No.  827,  specimen  on  the  left)  only  a  few 
pairs  of  jointed  appendages  are  seen,  but  a  ventral  view 
(No.  827,  specimen  on  the  right)  exposes  a  large  number 
of  these  paired  organs  extending  from  one  end  of  the 
body  to  the  other. 

The  preparation  (No.  828)  shows  more  plainly  the 
parts  that  make  up  the  external  skeleton.  There  are 
seven  distinct  segments  in  the  posterior  or  abdominal 


1  Chall.  Rep.,  Zool.,  XVI,  part   45,  1886,  p.  4. 

2  Brooks,  Johns  Hopkins  Univ.,  Stud.  Biol.  Lab.,  I.     In  this  vol- 
ume is  included  Chesapeake  Zool.  Lab.  Scientific  Results  of  season 
of  1878,  p.  152. 


METAZOA CRUSTACEA.  337 

region.  Six  of  these  are  similar,  while  the  seventh  or 
terminal  segment  is  larger,  rounder,  and  flattened  on  the 
edges.  The  five  anterior  abdominal  segments  carry  five 
pairs  of  similar  jointed  swimming-feet,  while  the  sixth 
bears  a  pair  of  modified  swimming-feet  The  slight  varia- 
tion in  the  structure  of  all  the  swimming-feet  excepting 
the  last  two  indicates  that  they  perform  a  similar  function. 
Each  swimming-foot  is  made  of  two  leaf-like  parts 
fastened  to  a  stem ;  the  former  are  fringed  with  long 
hairs.  Attached  to  the  base  of  each  swimming-foot  is  a 
gill  made  up  of  filaments.  The  last  pair  of  swimming- 
feet  are  longer  and  stronger  than  the  others.  They  con- 
sist of  more  sections  and  joints,  and  the  basal  section 
does  not  bear  a  gill.  These  two  swimming-feet  with  the 
large  terminal  segment,  which  is  without  appendages, 
constitute  an  efficient  organ  for  propelling  the  animal 
through  the  water. 

In  front  of  the  abdomen  are  four  similar  segments 
which  are  much  smaller  and  narrower  than  the  abdominal 
segments  already  described.  Three  of  these  segments 
bear  slender  little  organs  resembling  walking-legs,  while 
the  remaining  segment  bears  a  pair  of  appendages  very 
different  from  the  walking-legs,  but  similar  to  the  two 
pairs  of  appendages  in  front  of  them.  The  segments 
bearing  the  mouth  parts  and  one  pair  of  antennae  are 
consolidated  and  covered  in  part  by  the  carapace,  so 
that  the  number  can  only  be  inferred  by  the  number  of 
appendages. 

In  front  of  the  walking-feet  are  three  pairs  of  organs 
that  are  alike  in  shape  and  which  terminate  in  a  curved 
movable  jaw.  Then  come  the  large  grasping  organs  and 
in  front  of  them  a  slender  pair  of  appendages.  These 
five  pairs  are  the  maxillipeds.  In  front  of  the  maxillipeds 
are  three  pairs  of  small  maxillae  and  one  pair  of  short 
antennae. 

The  first  two  segments  of  the  body  bearing  the  eye- 
stalks  and  first  pair  of  antennae  are  freely  movable,  and 
in  this  respect  Squilla  differs  from  other  Crustacea. 


338  SYNOPTIC    COLLECTION. 

Having  found  twenty  pairs  of  appendages,  it  is  to  be 
inferred  that  there  are  twenty  segments  in  the  body. 
These  are  usually  divided  into  seven  abdominal,  eight 
thoracic,  and  six  cephalic. 

In  the  preparation  (No.  829)  the  nervous  system  is 
shown. 

Amphipoda.  Gammarus  locus ta  M.  Edw.  (No.  830 ; 
over  Section  12  large  figures  of  G.  ornatus  M.  Edw.),  like 
the  Amphipods  in  general,  has  a  body  made  up  of  similar 
segments  uncovered  by  a  carapace.  The  seven  abdom- 
inal segments  bear  the  six  pairs  of  swimming-feet,  the 
eight  thoracic  (the  first  one  of  which  is  represented  only 
by  remnants  of  its  ventral  and  lateral  portions)  bear  the 
thoracic  legs  and  maxillipeds.  The  eyes  of  Gammarus 
are  sessile  or  in  other  words  set  in  the  head.  Various 
parts  of  Gammarus  properly  labeled  are  drawn  on  a  large 
scale  in  the  plate  over  Section  12. 

Laemodipoda.  Caprella  (No.  831  ;  see  also  large 
figures  over  Section  12)  is  a  remarkable  crustacean  in 
appearance  when  seen  running  or  climbing  over  algae, 
hydroids,  or  starfishes.  The  body  is  made  mostly  of  the 
thoracic  region,  the  abdomen  being  reduced  to  a  mere 
tiny  knob.  The  long,  slender  segments  of  the  body  are 
distinct  and  so  loosely  put  together  at  the  joints  that  the 
animal  can  double  upon  itself.  At  the  forward  end  there 
are  two  pairs  of  antennae,  one  long  and  one  short,  which 
probably  aid  in  catching  food  (Gosse).  Back  of  these 
are  two  pairs  of  appendages  which  are  finely  adapted  for 
seizing  prey ;  the  last  section  but  one  is  enlarged,  while 
the  terminal  section  shuts  down  upon  it  as  the  blade  of  a 
pocket  knife  closes  into  the  handle. 

In  the  middle  of  the  body  two  pairs  of  respiratory- 
organs  take  the  place  of  feet ;  these  also  form  a  pouch 
for  the  young  during  the  season  of  oviferation.  At  the 
posterior  end  are  three  more  pairs  of  long  spiked  and 
bladed  feet  which  take  hold  of  objects  when  the  creature 
is  in  action. 


METAZOA  —  CRUSTACEA.  389 

One  of  the  external  parasitic  Crustacea  is  represented 
by  the  whale  louse,  Cyamus  ceti,  Latr.  (No.  832).  Its 
flattened  body  is  reduced  to  a  few  segments.  Most  of  the 
appendages  are  provided  with  hooks  whereby  the  crusta- 
cean fastens  itself  upon  the  whale.  This  is  the  case  with 
the  arms  which  have  no  claws,  but  the  movable  jaw  is 
modified  into  a  sharp  curved  hook.  The  third  and  fourth 
apparent  segments  bear  long  tubular  branchiae. 

Isopoda.  Idotea  wossnessenski  Brundt  (No.  833),  has 
the  body  flattened  from  above  and  divided  into  seven  dis- 
tinct thoracic  segments  and  an  indistinctly  segmented 
abdomen.  The  head  is  provided  with  a  pair  of  small 
sessile  eyes  and  two  pairs  of  antennae,  one  pair  being 
much  smaller  than  the  other.  Then  follow  seven  pairs  of 
similar  jointed  feet  placed  far  apart  on  the  lateral  edges 
of  the  ventral  side  and  adapted  for  walking.  Between 
these  legs  the  respiratory  leaves  are  snugly  folded  over 
the  eggs.  The  abdomen  is  supplied  with  leaf-like  swim- 
merets  and  the  first  pair  are  modified  into  a  cover  for  the 
other. 

The  segments  of  the  depressed  body  are  similar  from 
one  end  to  the  other,  there  being  slight  differentiation 
between  the  thoracic  and  the  abdominal  regions. 

The  head  with  its  pair  of  sessile  eyes  is  inconspicuous 
but  it  carries  one  pair  of  long  antennae.  The  thoracic 
region  has  three  pairs  of  jointed  feet  followed  by  two 
segments  without  feet,  and  these  in  turn  are  succeeded 
by  three  segments  with  feet.  The  respiratory  organs  are 
leaf-like  and  enclose  the  young  larvae.  The  thoracic 
appendages  are  followed  by  several  pairs  of  abdominal 
leaf-like  organs. 

The  fresh-water  Asellus  communis  Say  (No.  834)  is  a 
little  crustacean  with  a  long,  narrow,  depressed  body 
composed  of  similar  segments,  none  of  which  is  covered 
by  a  carapace.  The  head  is  provided  with  two  pairs  of 
antennae.  The  thorax  consists  of  seven  segments  and 
carries  seven  pairs  of  walking-feet.  The  terminal  seg- 


340  SYNOPTIC  -COLLECTION. 

ment  is  large  and  has  three  pairs  of  leaf-like  organs 
attached  to  the  ventral  side. 

The  many  peculiar  modifications  of  Serolis  (No.  835) 
are  interesting.  The  body  is  flattened  out  and  nearly 
circular  in  outline  as  compared  with  most  Crustacea. 
The  thoracic  segments  are  narrow  near  the  median  line 
and  spread  outward  and  downward  surrounding  the 
shortened  abdomen.  Neither  carapace  nor  rostrum  is 
present.  The  eyes  are  set  in  the  head  on  the  dorsal 
side  and  the  two  pairs  of  antennae  are  flattened  and 
closely  applied  to  the  thoracic  segments.  These  are  the 
only  appendages  visible 'from  above.  The  mouth  parts 
and  legs  are  all  flattened  and  the  latter  are  wide  apart 
on  the  edges  of  the  body. 

Lygia  dilatata  St.  (No.  836,  dried  specimen;  No.  837, 
alcoholic  specimen),  has  a  shortened  depressed  body  cov- 
ered like  most  of  its  kind  by  a  chitinous  exoskeleton. 
This  is  divided  into  a  small  number  of  segments  most  of 
which  are  distinctly  seen,  since  Lygia  has  no  carapace. 
The  head  is  small  and  fits  into  the  first  thoracic  segment, 
which  is  scooped  out  in  front  for  this  purpose. 

The  seven  thoracic  segments  are  similar  and  constitute 
the  larger  part  of  the  body,  while  the  six  visible  abdom- 
inal segments  are  narrow  and  are  crowded  closely 
together. 

The  thoracic  and  abdominal  segments  are  prolonged 
laterally  beyond  the  body  proper,  and  the  separate  side 
pieces  thus  formed  are  so  freely  movable  that  the  body 
can  double  upon  itself.  They  also  serve  to  protect  the 
appendages  (excepting  the  first  and  last  pair),  so  that 
these  are  not  seen  in  a  dorsal  view  (No.  836)  when  the 
crustacean  is  resting. 

The  eyes  are  compound  and  are  set  in  the  head.  One 
pair  of  antennae  are  long  and  the  other  pair  are  very 
short.  The  mouth  parts  are  small  and  compact.  The 
seven  pairs  of  jointed  thoracic  legs  perform  a  similar 
function  and  are  similar  in  structure. 


METAZOA CRUSTACEA.  341 

Packed  closely  together  under  the  abdomen  are  the 
leaf-like  respiratory  organs,  while  the  sixth  or  terminal 
abdominal  segment  bears  a  pair  of  caudal  appendages. 

MACROURA. 

Lucifer  (PL  838)  is  one  of  the  few  Macrouran  Crusta- 
cea which  pass  through  a  nauplius  stage  (PL  838,  fig.  i). 
It  possesses  at  this  time  the  three  pairs  of  locomotor 
appendages  and  an  ocellus,  but  as  yet  there  is  no  cara- 
pace nor  compound  eyes. 

The  nauplius  develops  into  the  zoe'a  stage  (fig.  2), 
when  the  antennae  and  mandibles  are  still  used  for  swim- 
ming. The  abdomen  and  its  telson  have  developed  and 
the  cephalothorax  is  provided  with  a  carapace. 

In  the  next  or  Schizopod  stage  (fig.  3)  the  antennae 
and  mandibles  have  lost  their  locomotive  function  and 
stalked  eyes  appear  with  the  ocellus. 

When  this  Schizopod  larva  moults  the  Mastigopus  or 
young  Lucifer  stage  (fig.  4)  reveals  a  marked  change  in 
the  forward  part  of  the  cephalothorax.  The  segments 
bearing  the  eye-stalks  and  two  pairs  of  antennae  are  car- 
ried far  forward,  while  the  hinder  segments  of  the  ceph- 
alothorax bear  the  mouth  parts  and  thoracic  legs.  The 
adult  does  not  differ  essentially  from  PL  838,  fig.  4.  The 
anterior  segments  extend  farther  forward  ;  the  first  pair 
of  thoracic  legs  are  vestigial,  while  the  remaining  four 
pairs  are  adapted  for  swimming,  being  abundantly  sup- 
plied with  hairs.  The  abdominal  appendages  borne  on 
the  six  abdominal  segments  also  aid  the  thoracic  legs  in 
swimming. 

Penaeus,  like  Lucifer,  leaves  the  egg  in  a  nauplius 
condition.  The  adult  Penaeus  canaliculatus  Oliv.  (No. 
839)  is  larger  than  most  shrimps  and  it  has  elaborated 
some  of  the  typical  features  of  this  group.  The  long 
pointed  rostrum  of  the  carapace  is  notched  on  the  upper 


342  SYNOPTIC    COLLECTION. 

side  like  a  saw  and  provided  with  short  hairs.  The  eyes 
are  prominent,  flattened,  and  black  in  color.  The  anten- 
nae are  the  most  conspicuous  organs,  the  scales  of  the 
second  pair  extending  beyond  the  rostrum.  These  organs 
and  the  mouth  parts  are  fringed  with  hairs,  giving  an  ele- 
gant appearance  to  Penaeus.  The  first  two  pairs  of  tho- 
racic legs  are  much  smaller  than  the  remaining  three 
pairs  and  are  provided  with  claws. 

The  abdomen  tapers  to  a  sharply  pointed  telson  and 
carries  good-sized  swimmerets  that  serve  as  a  protection 
for  the  masses  of  eggs. 

Most  of  the  groups  of  Crustacea,  although  composed 
largely  of  marine  forms,  yet  have  also  fresh-water  and 
terrestrial  members,  and  it  is  interesting  to  note  that  one 
species  of  Penaeus  (P.  brasiliensis  Latr.)  is  often  found 
in  brackish  waters,  and  even  ascends  streams  to  points 
where  the  water  is  nearly  or  quite  fresh.1 

The  fresh-water  prawn,  Palaemon  carcinus  Oliv.  (No. 
840,  on  upper  shelf)  is  remarkable  for  the  extreme  length 
of  its  antennae.  It  is  indeed  surprising  that  organs  of 
such  delicacy  and  length  can  be  of  use. 

The  second  pair  of  walking-feet  in  this  genus  are  the 
arms  and  claws,  and  these  are  also  greatly  prolonged. 
The  first  pair,  according  to  Gosse,2  are  used  as  brushes 
to  clean  the  ventral  side  of  the  thorax  and  abdomen. 
The  carapace  is  short  and  without  a  median  suture ;  it  is 
armed  in  front  with  an  elegant  curved  rostrum  having  a 
double  notched  edge.  In  the  species  Palaemon  serratus, 
Leach  found  that  the  point  of  the  rostrum  was  notched 
in  three  thousand  specimens,  while  the  notch  was  want- 
ing in  only  two  specimens,3  certainly  a  good  example  of 
the  persistency  of  a  structural  character.  The  eyes  of 
Palaemon  are  small  and  on  slender  stalks.  The  large 
swimmerets  of  the  abdomen  show  finely  in  No.  840. 

1  Stimpson,  Ann.  Lye.  Nat.  Hist.  N.  Y.,  X,  1874,  p.  133. 

2  Quoted  by  Adam  White,  Pop.  Hist.  Brit.  Crust.,  1857,  p.  131. 

3  Malac.  Podoph.  Brit.,  no.  15,  1817. 


METAZOA CRUSTACEA.  343 

Interesting  adaptive  characters  are  found  in  Alpheus 
heterochelis  Say  (PI.  841;  No.  842).  It  is  a  burrower  and 
one  of  its  arms  has  an  immense  claw  (No.  842)  which  is 
fully  as  large  as  the  cephalothorax.  The  wonder  is  that 
so  small  a  body  and  so  delicate  a  basal  portion  of  the 
appendage  can  control  the  movements  of  such  a  large 
organ.  That  this  organ  is  an  adaptation  of  the  adult 
animal  to  the  life  it  leads  is  proved  by  the  fact  that  in . 
the  young  Alpheus  (PI.  841,  fig.  i,  greatly  enlarged)  the 
claws  are  not  developed.  In  the  more  advanced  stage, 
however  (fig.  2,  enlarged),  they  are  of  considerable  size. 
Fig.  i  gives  the  color  of  the  young  Alpheus  which  changes 
with  growth  (fig.  2). 

In  Evatya  crassus  Smith  (No.  843),  the  abdomen  tapers 
and  the  last  segment  is  small.  The  swimmerets  of  the 
forward  segments  (excepting  those  of  the  first  segment) 
are  unusually  large,  broad,  and  hairy  organs.  The  small 
thoracic  legs  have  horny  spikes  at  their  ends.  Then 
comes  a  pair  of  enormously  developed  legs  covered  with 
dark  horny  knobs  ;  the  terminal  hooks  are  still  darker 
and  everything  indicates  that  these  organs  perform  hard 
work. 

The  eyes  of  this  species  are  inconspicuous  but  the 
second  pair  of  antennae  are  extremely  long  and  slender. 

The  shrimp  (Crangon  franciscorum  Stimp.)  (No.  844) 
has  the  segments  of  the  abdomen  tapering  to  a  long,  nar- 
row telson.  The  cephalothorax  is  small  and  the  rostrum 
weak.  The  swimmerets  are  long,  slender  organs  and  in 
one  of  the  specimens  (No.  844)  they  hold  the  mass  of 
eggs  in  place.  The  last  pair  of  swimmerets  are  large 
and  efficient  swimming  organs.  The  last  two  pairs  of 
legs  are  the  strongest  and  these  are  used  in  digging  holes 
when  the  shrimp  buries  itself  in  the  sand.  The  second 
and  third  thoracic  legs  are  slender  ;  they  are  not  provided 
with  claws  but  the  terminal  section  of  the  arms  bends 
upon  the  next  lower  section  like  the  blade  of  a  knife 
upon  the  handle.  The  antennae  have  large  basal  scales 


344  SYNOPTIC    COLLECTION. 

that  extend  forward  and  lie  horizontally,  concealing  from 
sight  the  two  arms  and  the  mouth  parts. 

Leach  says  that  Crangon  vulgaris  or  the  common 
shrimp  often  enters  estuaries,  especially  during  the  breed- 
ing season,  and  it  sometimes  ascends  rivers  with  the  tide 
and  is  left  in  great  quantities  in  the  saline  marshes. 

The  lobster,  Homarus  americanus  M.  Edw.  (PI.  845), 
passes  through  the  nauplius  state  in  the  egg,  and  when 
hatched  is  surrounded  by  a  thin  membrane  which  is 
moulted  before  the  little  creature  enters  upon  a  free- 
swimming  life.  The  first  larval  stage  (PL  845,  fig.  i)  is 
little  over  a  third  of  an  inch  long.  It  is  marked  by  the 
presence  of  a  comparatively  large  cephalothorax,  big 
compound  eyes,  and  a  prominent  frontal  spine ;  it  also 
has  a  segmented  abdomen  with  a  fan-like  telson.  The 
cephalothorax  bears  appendages  which  are  two-branched  ; 
the  outer  branch  or  paddle  is  flattened  and  provided  with 
long  hairs,  while  the  inner  branch  is  prehensile.  These 
appendages  resemble  the  swimming  organs  of  the  Schiz- 
opods  so  closely  that  this  stage  is  often  called  the 
Schizopod  larva.  The  abdomen  is  without  appendages, 
though  their  rudiments  can  be  seen  under  the  skin  from 
the  second  to  the  fifth  segments.  In  the  next  larval 
stage  (fig.  2)  the  cephalothorax  and  its  appendages  are 
similar  but  the  rudiments  of  abdominal  swimmerets  have 
developed.  At  the  fourth  moult  (fig.  3)  the  swimming 
paddles  are  reduced  to  vestiges  (fig.  4),  while  the  inner 
branches  have  developed  into  walking-legs.  The  lobster 
still  stays  at  the  surface,  swimming  forward  by  its  abdom- 
inal swimmerets  and  backward  by  its  abdomen.  At  the 
sixth  moult  the  thoracic  swimming  organs  are  wholly 
lost  and  before  the  seventh  moult  is  passed  the  lobster 
leaves  the  surface  of  the  sea,  going  to  the  bottom  and 
approaching  the  shore  where  it  lives  among  the  rocks. 
Its  larval  life  is  now  over.  During  the  first  year  the  lob- 
ster may  moult  from  fourteen  to  seventeen  times,  and  at 
the  end  of  this  time  it  is  from  two  to  three  inches  long. 


METAZOA CRUSTACEA.  345 

It  is  not  sexually  mature  until  it  is  ten  or  eleven  inches 
long  and  this  growth  probably  requires  four  or  five  years. 
It  exhibits  the  typical  crustacean  characters  on  a  large 
scale,  and  for  this  reason  we  shall  give  its  structure  in 
greater  detail,  thereby  summarizing  in  part  what  has 
already  been  said.  Many  of  these  characters  may  be 
seen  in  the  spiny  lobster,  Palinurus  ehrenbergi  Heller 
(No.  846),  and  in  the  preparation  (No.  847,  Homarus 
americanus  M.  Edw.).  The  cylindrical  body  is  covered 
by  a  hard  crust  or  exoskeleton  and  divided  into  two  dis- 
tinct regions,  the  cephalothorax  and  the  abdomen. 

The  abdomen  has  the  more  primitive  characters,  since 
its  six  circular  segments  and  seventh  flattened  segment 
are  distinct  and  movable.  To  each  of  the  six  segments 
is  attached  on  the  ventral  side  a  pair  of  appendages,  the 
swimmerets.  These  appendages,  excepting  the  first  and 
sixth  pairs,  are  composed  of  three  parts,  a  basal  stem  and 
two  leaf-like  portions.  Similarity  in  structure  suggests 
a  similarity  in  function,  and  we  find  that  these  organs  are 
used  in  swimming  forward  and  in  floating  from  below  up- 
ward. The  first  pair  of  swimmerets  is  modified  for 
reproductive  purposes,  and  the  last  pair,  which  are  larger 
and  stronger  than  the  others,  supplement  the  telson  and 
muscular  abdomen  in  propelling  the  animal  swiftly  back- 
ward through  the  water. 

The  cephalothoracic  segments  are  consolidated  so  that 
it  is  impossible  to  make  out  their  boundaries  with  absolute 
certainty.  They  are  mostly  covered  by  a  carapace  which 
bends  downward  on  the  sides,  covering  the  branchiae  or 
gills.  The  number  of  cephalothoracic  segments  can  be 
inferred  from  the  number  of  paired  appendages  attached 
to  it. 

In  front  of  the  swimmerets  are  four  pairs  of  walking- 
feet  which  are  jointed  in  such  a  manner  as  to  be  efficient 
organs  in  walking,  pushing,  and  pulling.  They  are  armed 
at  the  end  with  a  spike  (fourth  and  third  pairs  counting 
from  the  forward  end)  or  with  a  movable  and  useful  claw 


346  SYNOPTIC    COLLECTION. 

(second  and  first  pairs).  In  front  of  these  walking-legs 
there  are  a  pair  of  arms  which  in  the  embryo  cannot  be 
distinguished  from  the  other  walking-legs,  but  which  in 
course  of  development  twist  and  stretch  out  forward, 
becoming  arms  for  catching  food  and  for  anchoring. 

Sometimes  these  organs  through  injury,  by  accident, 
or  through  other  unfavorable  conditions,  become  de- 
formed and  often  in  such  cases  the  specimens  show  the 
strong  hereditary  tendency  possessed  by  the  claw  to  pro- 
duce its  like.  In  the  thirty-five  specimens  of  deformed 
lobsters' claws  in  the  collection  of  the  Boston  Society  of 
Natural  History  there  are  five  which  have  developed  an 
additional  claw  with  a  movable  jaw.  This  jaw  is  fastened 
invariably  either  to  the  immovable  jaw  of  the  lobster's 
claw  or  to  the  section  from  which  the  latter  grows.  In  no 
case  does  the  movable  jaw  make  a  mock  claw  with  the 
true  articulated  jaw. 

In  front  of  the  arms  are  the  three  pairs  of  maxillipeds 
and  one  pair  of  maxillae  which  are  used  in  obtaining 
food  and  carrying  it  to  the  mouth.  These  nine  pairs  of 
appendages  belong  to  the  thoracic  region.  The  seg- 
ments to  which  they  are  attached  are  immovably  con- 
solidated, as  we  have  said,  and  their  dorsal  portions  have 
disappeared,  owing  probably  to  the  fact  that  the  dorsal 
and  lateral  portions  of  the  fifth  segment  have  grown  out 
backward  in  the  form  of  a  carapace,  thereby  covering 
them  and  making  their  dorsal  portions  unnecessary. 

In  front  of  the  maxillae  is  another  pair  of  leaf-like 
maxillae  and  in  front  of  these  a  pair  of  hard  mandibles. 
The  mouth  parts  —  maxillipeds,  maxillae,  and  mandibles 
are  placed  snugly  together,  when  at  rest,  but  when  the 
animal  is  eating  they  are  all  in  active  motion. 

In  front  of  the  mouth  parts  are  the  two  pairs  of 
antennae,  one  long  and  one  short,  and  the  pair  of  mov- 
able eye-stalks  with  the  compound  eyes  at  their  ends. 
The  last  five  pairs  of  appendages  described  belong  to  the 
cephalic  region  and  their  segments  are  consolidated  like 


METAZOA CRUSTACEA.  347 

those  of  the  thoracic  region,  while  their  dorsal  and  lateral 
parts  extend  backward  to  form  the  protecting  carapace. 
Since  fourteen  pairs  of  appendages  have  been  found  at- 
tached to  the  cephalothorax,  this  part  is  supposed  to  be 
made  up  of  as  many  segments,  which  with  the  seven  ab- 
dominal segments  and  the  six  pairs  of  appendages  make 
in  all  twenty-one  segments  and  twenty  pairs  of  appendages. 

The  circulatory  system  of  the  lobster  is  shown  in  part 
in  the  preparation  (No.  847)  ;  portions  have  been  cut 
away  on  the  ventral  side,  exposing  the  sternal  artery 
which  gives  off  branches  that  pass  to  the  limbs. 

Nephrops  norwegius  Leach,  or  the  Norway  lobster  (No. 
848),  is  a  peculiarly  delicate  and  graceful  crustacean. 
The  cephalothoracic  region  is  more  slender  than  in  most 
genera  and  the  abdominal  segments  are  finely  sculptured. 
With  the  exception  of  the  sixth  pair  of  swimmerets  the 
appendages  are  likewise  long  and  slender  ;  especially  is 
this  true  of  the  second  pair  of  antennae  which  extend 
backward  beyond  the  body  and  are  thread-like  in  struc- 
ture. The  eyes  are  large  and  kidney-shaped,  while  the 
stalks  are  small. 

One  of  the  fresh-water  crustaceans  which  closely 
resembles  the  salt-water  lobster  in  structure  is  the  cray- 
fish, Cambarus  acutus  God.  (No.  849).  It  is  in  fact  a 
miniature  lobster  in  general  appearance,  having  the  same 
number  of  segments  and  appendages.  The  position  of 
the  legs  when  the  animal  is  walking  is  shown  in  the 
specimens.  The  body  of  the  male  (specimen  on  the 
left)  is  smaller  than  that  of  the  female  (specimen  on  the 
right),,  but  his  arms,  especially  the  claws,  are  much 
longer  than  hers.  The  fifth  pair  of  legs  are  without 
branchiae.  The  development  of  this  fresh-water  crusta- 
cean is  accelerated  and  the  nauplius  stage  is  passed 
through  in  the  egg,  evidence  of  which  is  found  in  the 
membrane  or  delicate  cuticle  that  is  formed  and  after- 
ward shed,  while  the  embryo  is  still  in  its  case.1  When 

1  Huxley,  The  Crayfish,  1880,  p.  215. 


348  SYNOPTIC    COLLECTION. 

hatched  the  crayfish  resembles  the  adult  in  general  char- 
acters, though  differing  in  details.  The  male  of  Cam- 
barus  has  two  forms  and  these  are  considered  by  Faxon1 
as  alternating  stages  in  the  life  of  the  same  individual, 
one  phase  being  assumed  through  the  breeding  periods, 
the  other  during  the  intervening  seasons  of  sexual  quies- 
cence. Crayfishes  abound  in  the  middle  and  western 
states,  but  few  know  that  they  are  also  found  in  Massa- 
chusetts. The  little  creature  seen  in  No.  850,  Cambarus 
bartoni  Gir.,  came  from  a  small  brook  in  North  Grafton 
where  for  a  number  of  years  we  obtained  theni  for  pur- 
poses of  instruction. 

Another  species  of  this  genus  is  the  blind  crayfish, 
Cambarus  pellucidus  Tellk.2  (No.  851)  found  "in  Mam- 
moth Cave.  Living  under  these  unfavorable  conditions 
its  body  is  smaller  and  the  eyes  which  its  ancestors  pos- 
sessed have  gradually  disappeared,  although  the  eye- 
stalks  remain  (Kingsley). 

Peculiar  modifications  of  structure  have  taken  place  in 
Galathea  rugosa  Fabr.  (No.  852).  The  exoskeleton  is 
ridged  and  many  of  the  ridges  are  provided  with  hairs. 
The  abdomen  is  shortened  and  tapers  posteriorly,  while 
the  cephalothorax  has  a  swollen,  puffed-out  appearance. 
The  latter  region  is  much  darker  in  color  at  the  anterior 
end  and  this  with  the  hairy  ridges  gives  the  crustacean 
a  hardy  aspect.  A  distinct  groove  on  each  side  of  the 
carapace  divides  this  protecting  covering  into  a  median 
and  two  lateral  parts.  The  last  thoracic  segment  is 
not  fastened  to  the  others  but  is  freely  movable. 

The  appendages  of  the  cephalothorax  like  the  body 
are  covered  with  hairs.  The  three  pairs  of  small  walk- 
ing-feet extend  forward  and  are  provided  with  spikes 
instead  of  claws  ;  the  last  pair  are  vestigial  and  are  not 


iAmer.  Journ.  Sci.,  (3),  XXVII,  1884,  pp.  42-44. 
3 Cambarus  pellucidus  Erichson.     Smith,  Rep.  U.  S.  Comm.  Fish 
and  Fisheries,  i872-'73,  p.  639. 


METAZOA CRUSTACEA.  349 

seen  in  a  dorsal  view,  since  they  are  doubled  up  within 
the  branchial  cavity,  and  are  attached  to  the  movable 
thoracic  segment. 

The  two  arms  are  similar  but  differ  greatly  from 
these  organs  in  other  genera.  The  sections  are  very 
nearly  the  same  in  breadth  and  terminate  in  a  claw,  the 
two  jaws  of  which  are  about  equal  in  size  and  armed 
with  sharp  fine  teeth.  The  arms  extend  straight  out  in 
front  as  seen  in  No.  852.  All  these  peculiarities  suggest 
that  the  habits  of  Galathea  are  very  different  from  those 
of  the  typical  Macroura. 

An  unusual  modification  of  the  external  skeleton  is 
found  in.  Callianassa  grandimana  Gibbes  (No.  853).  It 
is  membranous  and  looks  at  first  sight  as  if  it  were  the 
soft  unhardened  skin  which  appears  when  the  crustacean 
has  just  shed  its  crust  or  shell.  The  fossorial  habit  of 
living  in  tunnels  which  it  excavates  in  the  sand  is  doubt- 
less the  cause  for  this  condition  of  the  skeleton.  The 
tunnel  or  "tubular  domicile  "  extends  vertically  downward 
to  a  considerable  depth,  according  to  Say,1  and  its  com- 
pact sides  project  half  an  inch  or  more  above  the  surface, 
like  a  chimney  which  contracts  to  a  small  opening. 

Callianassa  has  a  long,  broad  abdomen  which  takes  up 
two  thirds  of  the  body.  The  cephalothorax  is  corre- 
spondingly short  and  the"  rostrum  consists  of  two  pieces 
hinged  to  the  carapace.  It  is  interesting  to  note  how 
the  terminal  sections  of  most  of  the  cephalothoracic  ap- 
pendages are  furnished  with  dark  brown  hairs  which 
grow  on  these  parts  that  perform  the  hardest  work  in 
digging. 

The  hermit  crab,  Eupagurus  (No.  854,  E.  bernhardus 
Brandt.;  No.  855,  the  same,  showing  nervous  system), 
is  a  modified  form  with  adaptive  characters.  The  young 
of  some  species  of  Eupagurus  have  a  symmetrical  abdo- 
men like  that  of  a  shrimp,  with  swimming-legs  on  the 

1  Journ.  Acad.  Nat.  Sci.  Phila.,  I,  1817,  p.  240. 


350  SYNOPTIC    COLLECTION. 

second,  third,  fourth,  and  fifth  segments,1  and  the  exter- 
nal skeleton  of  the  body  is  quite  firm. 

In  the  stage  preceding  the  moult  when  the  animal  seeks 
a  shell,  the  distinctly  segmented  abdomen  has  lost  its 
symmetry ;  the  feet  are  largest  on  the  right  side  and  the 
abdomen  begins  to  curve  away  from  the  longitudinal  axis. 
With  the  next  moult,  the  abdomen  is  soft  and  the  seg- 
ments indistinct,  while  some  of  the  abdominal  appendages 
are  lost  (PI.  856,  Eupagurus pollicaris} . 

The  adult  usually  lives  in  a  Gastropod  shell  (No.  854; 
No.  857,  Petrochirns  granulatus  Stimp.,  see  lower  shelf) 
and  in  this  way  the  abdomen  has  become  extremely  soft, 
light-colored,  and  indistinctly  segmented.  Its  appendages 
have  lost  all  those  characters  which  are  natatory,  and  have 
either  disappeared  or  have  taken  on  secondary  structural 
features.  Thus  the  first  segment  has  no  appendages ; 
the  second,  third,  and  fourth  have  limbs  on  the  left  side 
only  for  holding  the  eggs  during  the  egg-bearing  season  ; 
the  fifth  appendage  is  a  mere  vestige,  while  the  sixth  pair 
are  modified  for  holding  the  crab  in  its  shell. 

The  cephalothoracic  appendages,  though  less  modified 
than  the  abdominal,  still  have  undergone  changes  in 
structure.  The  arms  are  used  for  walking,  for  getting 
food,  and  for  closing  the  aperture  of  the  shell ;  the  second 
and  third  pairs  of  legs  for  walking  only,  while  the  fifth 
and  probably  the  fourth  pair  aid  in  holding  the  animal  in 
its  shell. 

Many  interesting  modificatioas  of  structure  may  be  seen 
in  the  burrowing  crustacean,  Hippa  talpoida  (No.  858  ; 
PL  859).  The  smooth,  more  or  less  tubular  cephalothorax 
is  well  fitted  for  a  burrowing  animal.  Four  of  the  abdo- 
minal segments  can  be  seen  from  above,  while  most  of 
the  remaining  portion  that  is  .bent  under  the  cephalo- 
thorax is  apparently  composed  of  one  piece,  the  segments 

1  Verrill,  Rep.  U.  S.  Comm.  Fish  and  Fisheries,  I,  i87i-'72,  p. 
530- 


METAZOA CRUSTACEA.  351 

having  become  consolidated  without  leaving  a  trace  of  the 
sutures,  in  this  way  a  wedge-shaped  implement  is  pro- 
duced which  is  an  efficient  organ  in  burrowing.  It  is  also 
aided  in  the  work  by  the  short,  stout  cephalothoracic  legs. 
Thus  equipped,  the  creature  burrows  backward  into  its 
hole  with  great  rapidity  and  is  wholly  hidden  save  the  tips 
of  its  small  antennae.1 

Although  the  adult  Hippa  is  more  of  a  burrower  than 
a  swimmer,  nevertheless  when  undisturbed  it  will  leave 
its  burrow  and  swim  about  by  means  of  its  thoracic  and 
abdominal  feet.  The  antennae  of  Hippa  are  unique 
organs.  When  extended  they  curve  like  the  horns  of  a 
deer  and  are  provided  with  long  hairs  on  the  outer  side. 
These  are  seen  in  No.  858,  but  more  plainly  in  PI.  859, 
where  they  are  extended.  When  living,  the  animal  usu- 
ally carries  them  folded  about  the  mouth,  and,  according 
to  Smith,  one  of  the  principal  offices  of  these  organs  is  to 
keep  the  anterior  appendages  —  mouth  parts,  etc.  —  free 
from  all  foreign  substances. 

A  relative  of  Hippa  is  found  in  Raninoides  levis  M. 
Edw.  (No.  860).  Here  the  entire  carapace  has  many 
irregular  serrated  markings.  The  front  edge  is  provided 
with  slender  pointed  teeth  and  the  rostrum  is  composed 
of  two  parts  and  appears  to  be  movable.  The  front  of 
the  cephalothorax  is  hairy.  The  last  pair  of  legs  are 
reduced  in  size  and  pushed  up  on  the  back.  The  arms 
have  become  flattened  and  twisted,  till  the  movable  jaw 
of  the  claw  is  inside  instead  of  outside  or  above. 

One  of  the  most  remarkable  and  interesting  modifica- 
tions of  structure  is  found  in  Dromia  vulgaris  M.  Edw. 
(No.  861),  which  lives  with  the  sponge  or  sometimes  in 
coral.  The  external  skeleton  has  become  soft  and  horny 

1  Smith,  Trans.  Conn.  Acad.  Arts  Sci.,  Ill,  1876,  pp.  311,  313. 
According  to  Verrill  (Rep.  U.  S.  Comm.  Fish  and  Fisheries,  I, 
i87i-'y2,  pp.  338,  339)  Hippa  talpoida  burrows  like  a  mole,  head 
first,  instead  of  backward. 


352  SYNOPTIC  "COLLECTION. 

and  is  covered  with  a  thick  coating  of  hairs  which  in 
color  and  texture  resemble  the  fibers  of  the  sponge.  In 
this  way,  whether  by  conscious  mimicry  or  by  an  instinc- 
tive adaptive  power,  the  crab  is  perfectly  protected. 

Even  the  naked  jaws  of  the  claws  are  not  hard  or  limy 
but  so  soft  that  they  crush  in  the  ringers.  According 
to  Bell1  the  young  have  the  carapace  entirely  covered 
with  a  sponge  which  also  conceals  the  two  hinder  pairs 
of  legs  as  these  are  pushed  above  the  others  and  are 
closely  pressed  against  the  back.  The  function  of  the 
legs  that  have  been  pushed  out  of  their  natural  position 
is  to  assist  in  holding  the  sponge  on  the  crab's  back,  and 
consequently  sharp  hooks  have  developed  at  their  ends. 

The  plump,  rounded  appearance  of  the  front  of  the 
cephalothorax  which  extends  forward  beyond  the  sponge, 
with  the  deep-set  eyes  in  their  circular  sockets,  gives  an 
almost  cat-like  expression  to  the  crab  which  is  amusing. 

The  little  Porcellana  ocellata  (No.  862)  is  interesting 
for  the  reason  that  its  telson  bears  a  pair  of  appendages. 
The  telson  itself  is  small  and  pointed ;  the  appendages 
are  fastened  to  it  on  its  sides  and  also  united  to  each 
other  in  the  median  line  behind  the  point  of  the  telson. 
These  appendages  with  those  of  the  sixth  abdominal  seg- 
ment, together  with  the  broad,  well-developed  abdomen 
which  turns  under  the  cephalothorax,  enable  this  little 
animal  to  swim*  hence  the  popular  name  of  "crab-lob- 
ster." But,  although  it  can  swim  on  occasion,  it  prefers 
to  stay  under  stones  or  in  narrow  crevices,  and  the  struc- 
ture of  its  body  is  well  adapted  to  such  an  environment, 
for  both  the  cephalothorax  and  abdomen  and  also  the 
appendages  give  one  the  impression  that  Porcellana  has 
been  pressed  out  flat. 

Lithodes  (No.  863,  placed  towards  the  back  of  the  Sec- 
tion) is  one  of  the  giant  crabs  of  the  group  represented 
by  the  hermit  crab.  Armed  with  spines  and  knobs  it  is 

1  Brit.  Stalk-eyed  Crustacea,  1853,  p.  371. 


METAZOA CRUSTACEA.  353 

a  formidable  animal.  The  small  abdomen  is  bent  under 
the  triangular  cephalothorax  so  that  it  resembles  that  of 
the  true  crab  soon  to  be  described.  There  are,  however, 
but  four  pairs  of  functionally  useful  walking-feet,  the  fifth 
pair  being  reduced  in  size  and  fastened  to  the  last  uncon- 
solidated  segment  of  the  cephalothorax,  as  in  the  hermit 
crabs.  Lithodes  has  given  up  the  habit  of  swimming  and 
is  found  creeping  along  the  bottom  with  sluggish  motion.1 

Birgus  latro  Linn.,  or  the  palm  crab,  is  an  animal  of 
great  interest,  since  it  has  not  only  changed  its  habitat 
from  the  sea  to  the  land  but  has  also  succeeded  -in  con- 
verting a  part  of  its  gill  chamber  into  an  air-breathing 
lung.  PL  864,  fig.  i,  is  a  diagrammatic  representation 
of  the  lungs  and  the  circulation  in  this  crab.  The  heart 
is  in  the  center  and  the  lung  cavities  on  either  side.  The 
anterior  blood  vessels  are  the  veins,  and  the  large  poste- 
rior vessel,  the  artery.  Fig.  2  is  a  diagram  of  a  vertical 
section  of  the  same,  showing  the  branchia  and  the  lung 
cavity  with  the  pulmonary  villi  or  tufts  on  the  inner  sur- 
face of  the  wall.  The  dark  circular  spots  are  blood  ves- 
sels which  have  been  cut  across  and  which  connect  with 
the  heart. 

This  crab  spends  its  adult  life  on  the  land  far  from 
water,  but  it  goes  to  the  sea  to  deposit  its  eggs  and  the 
young  are  free-swimming  creatures  which  breathe  the  air 
dissolved  in  water. 


BRACHYURA. 

The  development  of  our  common  crab,  Cancer  irroratus 
Say  (PI.  865;  Nos.  866-868),  illustrates  the  mode  of  devel- 
opment of  most  crabs.  The  nauplius  stage  is  passed 
through  in  the  egg,  the  crab  hatching  as  a  zoe'a  (PI.  865, 
fig.  i  ;  the  line  indicates  natural  size  ;  see  also  figure  on 

1  Dana,  Crustacea  U.  S.  Explor.  Exped.,  I,  1852,  p.  428. 


354  -      SYNOPTIC    COLLECTION. 

the  left  of  the  large  plate  over  Section  13).  The  three 
enlarged  figures  represent  different  stages  in  the  life  of 
the  young  crab.  In  this  larval  condition  the  plump, 
rounded  cephalothorax  is  provided  with  a  long  dorsal 
and  frontal  spine.  The  compound  eyes  are  sessile,  while 
the  appendages  of  both  regions  of  the  body  are  adapted 
for  swimming.  The  zoe'a  develops  into  the  so  called 
Megalops  stage  (PI/ 865,  fig.  2  ;  see  also  the  middle  fig- 
ure of  the  plate  over  section  13)  which  resembles  the 
lobster  in  the  general  shape  of  the  body.  The  append- 
ages of  the  abdomen  are  still  adapted  for  swimming,  but 
those  of  the  cephalothorax  have  become  transformed  into 
organs  for  walking  and  more  efficient  instruments  for 
catching  food.  The  claws  are  developed,  but  at  this 
stage  are  equal  in  size.  The  large,  compound  eyes  are 
now  on  short,  stout  eye-stalks. 

After  moulting  again,  this  swimming  animal  becomes  a 
walking  crustacean  and  is  found  at  the  bottom  (see  figure 
on  the  right  of  the  plate  over  Section  13). 

The  adult  crab  (Nos.  866-868)  is  a  fine  illustration  of 
concentration  of  parts  and  organs.  This  is  shown  most 
forcibly  when  this  animal  is  compared  with  the  lobster. 
Here  the  body  is  short,  broad,  and  flat.  The  abdomen  is 
reduced  to  a  thin,  small,  often  colorless,  and  altogether  in- 
significant part  of  the  body,  consisting  of  a  limited  number 
of  segments  and  usually  hidden  away  under  the  cephalo- 
thorax. Its  appendages  are  likewise  limited  in  number 
and  are  used  al  most  wholly  for  carrying  the  eggs.  The  ter- 
minal pair  of  swimmerets  has  disappeared  and  the  telson 
is  scarcely  more  than  a  vestige  of  its  former  self.  The 
reduction  of  the  abdomen  is  suggestive  of  the  cause  that 
has  produced  it ;  viz.,  the  change  of  habit  from  a  swim- 
ming to  a  walking  type  of  animal.  The  effects  of  this 
habit  are  still  further  illustrated  by  the  shape  of  the  ceph- 
alothorax and  the  structure  of  the  well  developed  walking- 
legs. 

All  the    appendages  of  the   cephalothorax  —  the  four 


METAZOA CRUSTACEA.  355 

pairs  of  walking-legs,  one  pair  of  arms,  six  pairs  of 
mouth  parts,  two  pairs  of  antennae,  and  one  pair  of  eye- 
stalks  —  although  the  same  in  number  as  in  the  lobster, 
are  crowded  together.  The  maxiliipeds  have  lost  their 
foot-like  appearance,  but  are  distinctly  mouth  organs, 
the  third  pair  being  folded  like  a  lid  over  the  other 
pairs. 

The  internal  structure  as  well  as  the  external  parts 
reveal  remarkable  concentration.  The  internal  skeletal 
portions  of  the  cephalothoracic  segments  are  consolidated 
(No.  866,  vertical  section),  while  the  carapace,  extending 
backward  on  the  dorsal  side,  covers  them  completely 
from  view.  The  nervous  system,  especially,  is  consolidated 
in  the  cephalothorax  in  a  most  surprising  manner.  No. 
867  exhibits  the  great  nerve  mass  in  the  center  of  this 
region  with  the  nerves  radiating  from  it  to  the  different 
parts  of  the  body.  The  stomach  and  intestine  belonging 
to  the  digestive  system  are  well  seen  in  No.  868. 

We  have  already  seen  that  the  Crustacea  offer  ex- 
tremely interesting  modifications  of  structure  brought 
about  by  the  varied  habits  of  the  animals.  There  still 
remain  in  the  Synoptic  Collection  numerous  examples  of 
Brachyura  which  have  been  chosen  to  illustrate  more 
fully  the  instructive  adaptations  of  this  group. 

Callinectes hastatus  Ord,the  "edible,"  "blue,"  or  "soft- 
shelled"  crab  (No.  869  ;  a,  male ;  b,  female)  can  swim 
rapidly,  and  for  this  purpose  the  last  pair  of  legs  is  con- 
verted into  a  pair  of  flattened  paddles.  These  are  such 
strong  organs  that  they  are  able  to  propel  the  body  for- 
ward in  spite  of  its  unwieldy  proportions. 

The  abdomen  of  the  male  tapers  abruptly  to  a  mere 
vestige  of  its  former  condition  and  lies  locked  by  two 
teeth  into  a  deep  groove  in  the  ventral  side  of  the  cepha- 
lothorax. The  abdomen  of  the  female,  on  the  other 
hand,  is  broad  and  adapted  for  carrying  the  eggs.  The 
sharply  notched  carapace  and  the  spiked  arms  of  this 
genus  offer  a  strong  defence  against  its  enemies. 


356  SYNOPTIC    COLLECTION. 

Eriphia  gonagra  M.  Edw.  (No.  870),  has  the  outer  side 
of  its  arms  and  the  forward  part  of  the  cephalothorax 
thickly  studded  with  knobs,  while  the  inner  and  ventral 
portions  of  the  arms  are  smooth.  The  eyes  in  this  genus 
are  wide  apart  and  the  front  of  the  cephalothorax  is 
broad,  while  the  region  as  a  whole  is  quadrilateral.  No. 
870  b,  c,  represent  the  male  "and  female.  The  most 
marked  difference  between  the  two  is  in  the  abdomen, 
that  of  the  male  (b)  being  small  and  narrow,  while  that 
of  the  female  (c)  is  broad  and  fringed  with  hairs  for  the 
purpose  of  carrying  the  eggs. 

Calappa  granulata  Fabr.  (No.  871),  has  a  convex  tri- 
angular carapace  with  its  greatest  breadth  at  the  pos- 
terior part.  It  is  light  in  color  with  a  luster  as  if  polished. 
The  abdomen  is  very  narrow  and  in  a  dorsal  view  wholly 
concealed  by  the  cephalothorax  and  carapace  which  also 
cover  the  largest  sections  of  the  legs.  The  claws  are 
unique  organs ;  they  are  flattened  vertically  and  the  im- 
movable section  of  the  claw  rises  higher  even  than  the 
cephalothorax. 

Corystes  dentatus  Fabr.  (No.  872),  is  one  of  those  crabs 
that  have  a  cephalothorax  longer  than  broad.  It  is 
found,  according  to  Bell,1  in  rather  deep  water  and  has 
the  habit  of  burying  itself  in  the  sand  with  the  exception 
of  the  tips  of  the  antennae.  It  is  evident  that  a  long, 
pointed,  more  or  less  tubular  cephalothorax  is  more  con- 
venient for  a  burrowing  animal  than  one  that  is  broad, 
flat,  and  truncated  at  the  forward  end.  The  body  is  light 
colored,  and  the  long,  slender  arms  extend  forward  rather 
than  sideways. 

Cardiosoma  guanhumi  Latr.  (No.  873),  has  a  hard, 
tough,  dark  brown  shell  covering  a  body  of  unusual 
thickness,  and  also  its  prodigious  right  arm  which  in  the 
male  is  out  of  all  proportion  to  the  rest  of  the  appendages. 
The  claw  is  provided  with  two  blunt,  knob-like  teeth  placed 

^rit.  Stalk-eyed  Crustacea,  1853,  p.  161. 


METAZOA CRUSTACEA.  357 

opposite  each  other ;  the  other  teeth  are  minute  and  can 
be  of  little  use.  The  eye-stalks  are  long  and  prominent 
and  when  the  animal  is  alarmed  it  withdraws  them  into 
deep  sockets. 

Pseudothelphusa  dentata  Latr.  (No.  874),  looks  brown 
and  hardy  as  if  it  were  accustomed  to  weathering  storms. 
The  cephalothorax  is  nearly  triangular  in  form,  with  a 
broad,  straight  front,  tapering  posteriorly  towards  the  ab- 
domen. The  first  segment  of  this  region  is  narrow  and  is 
flanked  on  either  side  by  the  basal  joint  of  the  fifth  pair 
of  legs,  but  the  remaining  segments  in  the  female  broaden 
out  for  use  in  the  breeding  season.  The  arms  are  for- 
midable looking  organs  and  in  this  case  the  left  arm  is 
larger  than  the  right.  The  abdomen  in  the  walking  crabs 
is  bent  under  the  cephalothorax,  as  we  have  already  seen, 
and  therefore  cannot  be  used  as  a  locomotor  organ.  It 
is,  in  fact,  of  little  use  excepting  in  the  female,  where  it 
serves  as  a  cover  for  the  eggs  which  are  fastened  to  its 
appendages.  We  should  expect,  therefore,  to  find  this 
part  in  the  female  much  more  developed  than  in  the 
male,  and  this  is  the  case,  as  shown  by  Grapsus  macu- 
latus  Catesby  (No. 875). 

The  cephalothorax  of  this  crab  is  unusually  flattened  ; 
it  approaches  a  circular  form  excepting  in  front  where  it 
is  truncated.  All  the  parts  are  clearly  seen  in  No.  876, 
which  is  a  dissection  to  show  the  exoskeleton.  The 
seven  segments  of  the  abdomen  are  unusually  large  and 
the  four  pairs  of  hairy  appendages  are  of  considerable 
size.  In  this  crab  the  three  hinder  pairs  of  walking-legs 
are  the  largest,  while  the  second  pair  is  comparatively 
small  and  the  arms  are  short  and  stout.  The  six  pairs  of 
mouth  parts  are  similar  to  those  of  most  crabs,  but  the 
antennae  are  extremely  minute  and  the  eye-stalks  are 
short.  The  sternal  portion  of  the  cephalothorax  with  the 
genital  openings  on  the  third  segment  are  seen  in  the 
preparation.  The  front  portion  of  this  region  of  the  body 
bends  vertically  downward,  giving  the  truncated  appear- 


358  SYNOPTIC    COLLECTION. 

ance  to  the  otherwise  circular  outline,  as  already  pointed 
out. 

The  carapace  sometimes  becomes  ornamented  with 
spines,  as  seen  in  Pericera  cornuta  M.  Edw.  (No.  877). 
Two  long  divergent  spines  extend  forward,  while  the  next 
longer  pair  protect  the  closed  tubes  for  the  eye-stalks. 
The  walking-legs  (not  seen  in  the  specimen)  are  free 
from  spines.1 

The  spider  crab,  Metoporhapis  calcarata  Stimp.  (No. 
878),  resembles  a  spider  in  having  a  small  cephalothorax 
and  extremely  long  legs.  The  former  appears  to  have 
been  pushed  upward  in  front,  so  that  the  slender,  sharp 
rostrum,  instead  of  extending  forward  as  in  most  Crus- 
tacea, points  almost  vertically  upward.  The  posterior 
part  of  the  cephalothorax.  also  appears  to  have  been 
crowded  upward  and  forward  with  the  result  of  bringing 
the  last  or  fourth  pair  of  legs  very  nearly  over  the  third 
pair.  In  the  process  the  carapace  has  been  shortened, 
so  that  the  last  segment  of  the  thorax  is  exposed.  The 
arms  with  their  claws  are  slender  and  extend  forward. 
The  rostrum  and  the  large  spikes  of  the  legs  are  tipped 
with  two  tiny  spines. 

,A  relative  of  the  spider  crab  is  Dorippe  lanata  Bosc. 
(No.  879).  In  this  case  the  hind  pair  of  walking-legs 
are  pushed  up  on  the  back  and  being  of  no  use  for  loco- 
motion in  this  position  they  have  become  vestigial.  The 
third  pair  of  legs  are  undergoing  the  same  process,  being 
much  smaller  and  shorter  than  the  first  and  second  pairs. 
The  latter  are  long  and  spider-like.  The  claws  are  little 
organs  and  their  position  indicates  that  they  offer  efficient 
aid  to  the  mouth  parts. 

One  species  of  Dorippe  (D.  facchino)  is  of  especial 
interest,  since  it  is  never  found  without  a  sea-anemone 
(Cancrisocia  expansa  St.)  on  its  back.  This  is  an  admir- 
able illustration  of  commensalism,  since  neither  animal 
is  ever  found  excepting  in  each  other's  company. 

1  Miers,  Journ.  Linn.  Soc.  London,  XIV,  1879,  p.  664. 


METAZOA CRUSTACEA.  359 

Ixa  (No.  880)  is  protected  by  a  sharp  pointed  spike 
which  extends  outward  on  either  side  of  the  cephalo- 
thorax.  The  arms  are  flattened  vertically  so  that  the 
movable  jaw  of  each  claw  moves  up  and  down  instead  of 
horizontally.  These  organs  when  at  rest  are  folded  over 
the  front  of  the  ventral  side  of  the  carapace  and  have  the 
same  knobs  and  markings,  as  seen  in  No.  870. 

Maia  squinado  Latr.  (No.  88 1),  has  a  spiny  and  hairy 
cephalothorax  that  is  pointed  in  front  and  extremely  nar 
row  behind  where  it  passes  into  the  flat  and  spineless  but 
hairy  abdomen.  The  arms  in  Maia  are  surprisingly 
small  and  weak,  while  the  claws  are  almost  wholly  free 
from  spikes  and  hairs,  although  the  walking-legs  are  all 
hairy.  According  to  Leach,  Maia  is  extremely  common 
in  deep  water  and  is  called  by  the  fishermen  the  thorn- 
back.  This  same  author  states  that  the  young  often 
approach  the  shore. 

Belonging  to  the  same  family  of  spider  crabs  as  Maia 
is  Hyas  araneus  Leach  (No.  882) ,  which  has  a  carapace 
without  spines  and  the  four  pairs  of  walking-legs  well 
developed. 

The  reduction  of  the  walking-legs  is  carried  still  further 
in  Lambrus  (No.  883).  Although  most  of  these  organs 
are  wanting  in  the  specimen,  yet  enough  of  one  leg  is  left 
on  the  right  side  to  show  how  short,  small,  and  smooth 
they  have  become.  The  arms,  on  the  other  hand,  are 
more  than  three  times  the  breadth  of  the  cephalothorax. 
and  are  provided  with  spines  from  one  end  to  the  other, 

Another  peculiarly  modified  form  is  Cryptopodia  forni- 
cata  M.  Edw.  (No.  884),  in  which  nothing  but  the  cara- 
pace, arms,  and  small,  partly  hidden  eyes  are  to  be  seen 
in  a  dorsal  view.  The  walking-legs  are  wholly  concealed 
by  the  carapace  that  is  greatly  extended  laterally.  The 
eyes  are  protected  by  the  flattened  rostrum  which  has  a 
row  of  tiny  dots  along  its  edge. 

The  fiddler  crab,  Gelasimus  vocator  Martens  (No.  885), 
is  a  small  crab  with  a  quadrangular  cephalothorax  and  in 


360  SYNOPTIC    COLLECTION. 

the  female  (No.  885,  c,  d)  a  broad  rounded  abdomen  (c). 
The  arms  in  this  sex  are  similar;  both  are  small  with 
small  claws  (c,  d).  The  males  (No.  885,  a,  b,  e,  f),  how- 
ever, have  one  arm  much  larger  than  the  other,  while  the 
claw  is  greatly  developed.  This  arm  may  be  on  the  right 
side  (b)  or  on  the  left  (a,  e,  f).  It  is  carried  across  the 
front  of  the  body  in  a  somewhat  similar  position  to  that  of 
the  arm  of  a  tiddler,  hence  the  name  of  fiddler  crab. 
The  movable  jaw  of  the  big  claw  in  (f)  has  apparently 
been  broken  off  and  another  piece  has  grown  out  and 
beyond  the  immovable  jaw.  These  crabs  are  fighters  and 
often  an  arm  is  lost  in  the  .fray.  They  walk  and  run  side- 
ways, but  they  spend  much  of  their  time  in  burrows  which 
they  make  by  removing  the  sand  and  carrying  it  out  of 
the  opening  with  the  three  anterior  legs  on  the  rear  side, 
while  they  climb  out  of  the  burrow  by  the  legs  of  the  side 
in  front.  This  front  side  may  be  either  the  right  or  the 
left  side  of  the  crab,  but  in  the  male  it  is  usually  the  side 
with  the  big  claw. 

Gonoplax  rhomboides  Desm.  (No.  886),  like  Gelasimus 
has  a  four-sided  cephalothorax  with  the  greatest  breadth 
in  front.  The  stalked  eyes  extend  out  laterally  nearly  to 
the  edge  of  the  carapace.  The  arms  are  long,  slender 
organs,  as  is  the  case  with  some  burrowers,  Gonoplax 
having  the  habit  of  excavating  burrows  in  the  hardened 
clay  which  are  open  at  either  end. 

It  has  been  shown  that  the  Crustacea  offer  numerous 
and  remarkable  examples  of  adaptation  of  structure  to 
habit.  They  are  also  instructive  in  showing  how  a  swim- 
ming type  of  animal  may  be  converted  into  a  walking 
type.  In  this  process  the  law  of  cephalization  or  head- 
development  operates,  and  the  organs,  especially  the 
nerves  and  ganglia,  are  concentrated  in  the  anterior  part 
of  the  body.  They  possess  many  characters  in  common 
with  the  next  group,  the  Arachnozoa. 


METAZOA ARACHNOZOA.  361 


ARACHNOZOA. 


Section  14  (in  part). 

Trilobita.  The  trilobites  and  the  king  or  horseshoe 
crabs  with  their  allies,  the  Arachnida,  form  a  group  inter- 
mediate between  the  Crustacea  and  Myriopoda.  Trilo- 
bites are  primitive  in  structure  and  offer  good  illustrations 
of  generalized  segmented  animals  bearing  jointed  append- 
ages. They  also  constitute  one  of  the  few  groups  which 
well  illustrate  a  natural  classification.  As  Beecher  *  has 
pointed  out,  the  principles  of  such  a  classification  can  be 
best  applied  in  a  group  of  animals  which  has  a  geological 
history  more  or  less  complete,  and  which  is  not  wholly 
parasitic  or  greatly  reduced. 

The  trilobites  have  a  long  geological  history  covering 
the  time  from  the  pre-Cambrian  to  the  Permian.  Their 
structure  is  generalized  and  quite  uniform,  and  no  sessile, 
stalked,  parasitic,  fresh-water,  or  land  species  is  known. 
We  are  therefore  dealing  with  primitive,  free-swimming, 
marine  forms. 

The  stage  in  trilobites  corresponding  to  the  protoconch 
of  Cephalopods  and  the  protegulum  of  Brachiopods  is 
known  as  the  protaspis  (PI.  887,  fig.  I,  Sao  hirsuta  Bar- 
rande).  At  this  time  the  trilobite  consists  almost  wholly 
of  the  head  region  or  cephalon,  covered  by  a  dorsal 
shield  and  with  a  central  axis  clearly  defined.  The  ab- 
dominal segments  —  which  consolidated  are  called  the 
caudal  shield  or  pygidium  —  are  now  only  indistinctly 
outlined.  The  free  cheeks  are  situated  on  the  ventral 
side  and  therefore  cannot  be  seen  in  a  dorsal  view  ;  only 
the  eye-lines  which  in  older  stages  extend  from  the  central 
axis  to  the  eyes  are  now  visible  from  above  (see  fig.  i). 

1  Amer.  Journ.  Sci.,  (4),  III,  March,  1897,  pp.  97,  98. 


362  SYNOPTIC    COLLECTION. 

In  an  older  protaspis  (fig.  2,  x  30)  the  central  axis  is 
segmented  ;  the  pygidium  has  developed,  and  is  distinctly 
segmented.  The  free  cheeks,  though  narrow,  are  at  the 
margin  so  that  they  can  be  seen  in  a  dorsal  view  (fig.  2). 
In  a  still  older  protaspis  (fig.  3,  x  30)  the  pygidium  is 
complete  but  the  thoracic  segments  are  not  yet  formed. 
When  the  protaspis  stage  has  passed  into  the  nepionic 
stage  the  eyes  and  free  cheeks  have  migrated  to  the  dor- 
sal side  of  the  cephalon  (fig.  4,  cephalon,  pygidium  not 
drawn.  The  shaded  parts  are  the  free  cheeks;  the  cres- 
cent eyes  are  seen  at  the  ends  of  the  eye-lines). 

The  thoracic  segments  form  between  the  cephalon  and 
pygidium,  as  seen  in  the  adult  (fig.  6,  x  £).  They  are 
freely  movable,  while  those  of  the  caudal  shield  are  con- 
solidated. The  free  cheeks  become  larger  and  the  eyes 
are  farther  from  the  margin  (fig.  5).  The  central  portion 
of  the  head  region,  or  in  other  words,  the  forward  part  of 
the  axis,  is  known  as  the  glabella,  and  the  fixed  cheeks 
are  situated  between  this  part  and  the  free  cheeks.  Other 
characters  of  the  adult  trilobite  are  better  seen  in  Triar- 
thrus,  the  next  genus  to  be  described. 

The  protaspis  of  Triarthrus  differs  somewhat  from  that 
of  Sao,  since  the  central  axis  of  the  cephalon  does  not 
extend  to  the  anterior  edge  (PI.  888,  fig.  i),  and  the  eye- 
lines  run  from  the  first  segment  to  the  margin.  A  resto- 
ration of  the  ventral  sida  of  the  protaspis  at  this  time  is 
represented  in  fig.  2.  Since  the  head  region  has  five 
segments  it  is  inferred  tha"t  it  has  as  many  pairs  of  ap- 
pendages, and  that  the  pygidium  has  two  pairs  for  the 
same  reason.  The  first  pair  of  appendages  are  un- 
branched  and  are  probably  sense  organs,  but  the  remain- 
ing pairs  are  two-branched  and  adapted  for  swimming. 
The  segments  of  the  pygidium  increase  in  number,  as 
seen  in  fig.  3. 

The  adult  (No.  889  ;  Nos.  890,  891,  models  ;  also  PI. 
888,  fig.  4)  has  a  small  cephalon,  while  the  thoracic  and 
abdominal  regions  are  divided  into  distinct  segments  (No. 


METAZOA ARACHNOZOA.  363 

890,  dorsal  side).  The  body  is  also  divided  longitudinally 
into  three  lobes — central  axis  with  pleurae  on  either  side 
—  and  hence  the  name  of  trilobite. 

The  cephalon  is  provided  with  compound  unstalked 
eyes.  These  eyes  have  migrated,  as  we  have  already 
said,  from  the  ventral  side  over  the  margin  and  are  now 
on  the  inner  side  of  the  free  cheeks  some  distance  from 
the  margin.  Each  segment  bears  a  pair  of  appendages, 
most  of  which  are  similar  in  structure  and  adapted  for 
swimming  or  for  crawling  on  the  sea  bottom. 

In  front  a  pair  of  long,  jointed  antennae  have  been  dis- 
covered. These  are  clearly  seen  extending  forward  in 
No.  889,  a  specimen  taken  from  the  lower  Silurian  forma- 
tion. 

A  deep  groove  runs  through  the  middle  of  the  ventral 
side  of  Triarthrus  becki  (No.  891),  and  the  mouth  parts 
and  long,  jointed  feet  fastened  to  the  axis  conceal  the  tri- 
lobed  character  of  the  body.  These  feet  are  made  up  of 
a  stem  and  two  branches,  one  of  which  is  adapted  for 
swimming,  having  long  hairs,  while  the  other  is  fitted  for 
crawling.  The  appendages  of  the  pygidium  are  especially 
fitted  for  locomotion,  having  flattened  leaf-like  sections 
and  very  long  hairs. 

According  to  Beecher1  no  traces  of  any  special  respir- 
atory organs  have  been  found  in  Triarthrus  and  their  ex- 
istence is  doubtful,  though  the  fringes  on  the  locomotor 
organs  may  have  served  as  gills,  since  in  many  forms  the 
functions  of  locomotion  and  respiration  were  combined. 

In  some  genera  of  trilobites  the  central  axis  is  broad, 
while  the  cephalon  is  small  and  granulated,  as  seen  in 
Lichas  boltoni  Hall  (No.  892).  Many  of  the  hairy  ap- 
pendages are  well  preserved  in  this  fossil,  and  are  seen 
lying  on  either  side  of  the  large  flat  body.  The  glabella 
has  a  swollen  lobe  in  front  besides  lateral  lobes,  and  the 
eyes  are  seen  near  the  margin. 

1  Amer.  Journ.  Sci.,  (4),  I,  April,  1896,  p.  253. 


364  SYNOPTIC    COLLECTION. 

In  the  large  order  with  Triarthrus  and  Lichas,  is  found 
Isotelus  gigas  Dekay  (No.  893).  This  genus  exhibits  the 
three  regions  of  the  body  very  distinctly.  The  cephalon 
and  caudal  shield  are  smooth  and  unornamented,  showing 
only  slight  evidence  of  segmentation.  The  eight  thoracic 
segments,  on  the  other  hand,  are  distinct.  The  central 
axis  is  unusually  broad  in  this  genus  and  the  glabella  is 
not  lobed.  Close  to  the  glabella,  on  either  side,  the  eyes 
stand  out  prominently  (No.  893).  These  trilobites  had 
the  habit  of  doubling  upon  themselves  (No.  894),  prob- 
ably for  safety.  If  this  specimen  were  turned  over,  the 
posterior  part  of  the  dorsal  side  would  be  seen  as  repre- 
sented by  the  figure  (PI.  895).  When  doubled  up  in  this 
way  the  ventral  side  of  the  animal  is  completely  hidden. 

In  the  most  specialized  order,  as  given  by  Beecher,  we 
have  Calymene  (No.  896)  and  Dalmanites  (No.  897). 

The  body  in  Calymene  is  more  or  less  ornamented. 
The  thoracic  region  is  the  longest,  consisting  of  thirteen 
segments,  while  the  caudal  shield  is  tapering  and  bends 
downward  at  nearly  right  angles  to  the  body.  The  gla- 
bella is  deeply  grooved  (No.  896)  and  its  lobes  are  some- 
times mistaken  for  eyes.  The  latter  organs  are  on  the 
free  cheeks  and  are  comparatively  small. 

The  body  of  Dalmanites  (No.  897,  D.  limuJurus  Hall) 
extends  backward  in  a  long  spine  (not  shown  in  the 
specimen).  The  dorsal  shield  is  also  carried  back  on 
each  side  as  a  sharp  spine.  The  eyes  in  this  genus  are 
generally  large  and  are  always  faceted.  The  free  cheeks 
on  which  they  are  borne  unite  in  front,  making  a  com- 
plete segment  which  Beecher  regards  as  the  ocular  seg- 
ment. 

Merostomata.  The  horseshoe  or  king  crab,  Limulus 
polyphemus  Latr.  (No.  898;  PI.  899;  Nos.  900-903), 
is  the  only  representative  of  the  Merostomata  that  is 
living  at  the  present  time.  In  its  development  it  passes 
threugh  a  trilobite  stage.  This  is  seen  in  No.  898  and 
in  PI.  899,  figs.  1-3.  The  dorsal  view  of  the  embryo  just 


METAZOA ARACHNOZOA.  365 

before  hatching  (fig.  i)  shows  the  anterior  region  (which 
in  this  case  is  the  cephalothorax)  and  the  three-lobed 
abdomen.  The  anterior  segments  of  the  abdomen  at  this 
stage  are  separate,  and  the  posterior  part  has  segments 
that  are  distinctly  seen.  The  ventral  view  of  the  same 
embryo  (fig.  2)  exhibits  the  six  pairs  of  appendages 
attached  to  the  cephalothorax  (also  seen  in  fig.  3,  side 
view)  and  two  pairs  of  leaf-like  organs  to  the  abdomen 
(ng-  2). 

The  adult  Limulus  (No.  900.  A,  dorsal  side  ;  B,  ventral 
side)  is  protected  by  a  chitinous  exoskeleton,  the  parts  of 
which  have  been  separated  in  the  preparation  (C).  The 
cephalothoracic  region  is  horseshoe-shaped,  while  the 
abdomen  lies  behind  and  extends  backward  into  a  long, 
sharp,  movable  spine.  A  flexible  membrane  at  the  junc- 
tion of  the  cephalothorax  with  the  abdomen  enables  the 
animal  to  bend  its  body.  Traces  of  segmentation  are  seen 
on  the  dorsal  side  of  the  cephalothorax  (No.  900,  A)  and 
more  plainly  on  the  abdomen,  where  seven  segments  can 
be  made  out  in  part.  The  consolidated  portion  behind 
these  segments  is  supposed  to  consist  of  five  segments 
soldered  together  so  that  even  their  sutures  are  lost. 

Limulus  has  a  pair  of  single  eyes  situated  one  on 
either  side  of  the  anterior  median  spine.  The  compound 
eyes  are  aggregations  of  single  eyes  and  quite  different 
from  the  more  specialized  compound  eyes  of  Crustacea 
and  insects.  They  are  situated  far  back  on  the  cephalo- 
thorax and  are  widely  separated. 

The  cephalothorax  bears  six  pairs  of  appendages  and 
the  short  metastoma  or  under  lip  situated  back  of  the 
mouth  (No.  900,  C) .  The  first  pair  of  appendages  are 
in  front  of  the  mouth  and  bend  backward  over  the  open- 
ing. The  succeeding  five  pairs  are  adapted  for  walking 
and  seizing  food.  All  excepting  the  sixth  pair,  which  is 
used  in  pushing  and  in  propping  up  the  body,  terminate 
in  a  claw,  and  their  inner  section  carries  a  leaf-like  part 
thickly  covered  with  hair. 


366  SYNOPTIC    COLLECTION. 

The  spines  on  the  sides  of  the  abdomen  differ  from 
those  on  other  parts  of  the  body  by  being  movable.  The 
abdomen  is  provided  with  a  so  called  operculum  which 
consists  of  a  pair  of  appendages  soldered  together  and  of 
five  pairs  of  thin  plate  like  swimmerets  (No.  900,  C) 
chiefly  used  as  respiratory  organs.  On  the  under  side  of 
these  plates  are  hundreds  of  leaves  which  are  supplied 
with  blood  vessels. 

The  tubular  heart  with  the  larger  blood  vessels  is 
seen  in  the  preparation  (No.  901).  The  upper  portion 
of  the  exoskeleton  has  been  cut  away  and  the  circulatory 
organs  distended  with  wax.  In  No.  902  the  arteries 
which  arise  from  the  anterior  end  of  the  heart  are  ex- 
posed. These  unite  to  form  the  sternal  artery.  The 
latter  is  seen  in  the  preparation  No.  903  with  the 
branches  that  run  to  the  limbs. 

Allied  to  the  Merostoma  on  the  one  hand  and  to  the 
Arachnida  on  the  other  are  the  Eurypterids,  of  which 
Pterygotus  bilobus  Salt.  (No.  904)  is  a  representative. 
The  body  is  long  and  distinctly  segmented,  excepting  the 
forward  part  which  is  covered  by  the  small,  short  cara- 
pace. 

The  first  pair  of  appendages  are  in  front  of  the  mouth, 
as  in  the  trilobites,  and  are  provided  with  claws.  These 
are  followed  by  several  pairs  which  were  used  for  catch- 
ing food  and  for  locomotion,  while  the  largest  pair,  which 
extend  outward  on  either  side  like  wings,  were  powerful 
swimming  organs. 

ARACHNIDA. 

The  resemblances  between  Limulus  and  the  scorpion  of 
the  Arachnida  are  shown  in  the  preparations  (Nos".  905, 
906).  The  cephalothorax  of  both  animals  is  probably 
made  of  six  segments,  while  there  are  twelve  in  the  abdo- 
men. 


METAZOA  —  ARACHNOZOA.  367 

The  single  eyes  are  in  the  anterior  part  of  the  cephalo- 
thorax,  but  in  the  scorpion  there  are  three  pairs  on  the 
anterior  edge  and  one  pair  situated  farther  back. 

The  number  of  appendages  attached  to  the  cephalo- 
thorax  and  abdomen  is  the  same  (Nos.  905,906).  These 
consist  of  a  pair  of  mandibles,  or  chelae  as  they  are  called 
in  the  scorpion ;  a  pair  of  maxillae  or  pedipalpi,  provided 
in  the  scorpion  with  nippers ;  and  four  pairs  of  similar 
walking-legs  (in  the  preparation  one  leg  is  wanting). 
The  first  pair  of  abdominal  appendages  are  represented 
in  both  animals  by  the  operculum  which  conceals  the 
median  genital  opening.  The  second  pair  have  become 
peculiarly  modified  in  the  scorpion  to  form  comb-like 
organs  (see  No.  906)  which  are  probably  tactile  in  func- 
tion (Shipley).  The  four  following  abdominal  segments 
of  the  scorpion  have  slit-like  openings  or  spiracles  which 
lead  into  sacs  containing  the  breathing  organs  or  lung- 
books.  There  are  four  pairs  of  these  internal  organs 
(No.  906),  each  consisting  of  hundreds  of  leaves.  The 
embryo  scorpion  has  external  appendages  on  these  seg- 
ments bftt  in  the  process  of  development  they  are  re- 
placed by  the  lung  sacs.  The  latter  organs  therefore 
correspond  to  the  last  four  pairs  of  external  branchiae  of 
Limulus. 

The  terminal,  postanal  section  of  the  scorpion  is  pro- 
vided with  two  poison  glands,  and  the  poison  is  dis- 
charged through  the  opening  at  the  end  of  the  sharp, 
pointed  spine  which  is  in  reality  the  poison  fang. 

The  spiders  are  the  most  specialized  of  the  Arachnida. 
This  specialization  is  shown  most  strikingly  in  the  adult 
condition,  while  the  embryo  spider  exhibits  certain  char- 
acters possessed  by  the  scorpions  and  probably  by  the 
earliest  ancestors  of  the  group.  The  adult  is  without 
even  vestiges  of  abdominal  legs,  but  the  embryo  has  them 
clearly  marked  (PI.  907,  fig.  i,  Clubione  coiled,  and  fig. 
2,  the  same  unrolled)  as  six  pairs  of  bud-like  projections. 
The  four  pairs  of  cephalothoracic  feet  and  the  two  pairs 


368  SYNOPTIC    COLLECTION. 

of  mouth  parts  are  indicated  at  this  stage  by  larger  buds 
(figs,  i,  2).  The  latter  continue  to  grow,  while  the  ab- 
dominal feet  are  soon  lost. 

Comparatively  speaking,  the  order  of  Arachnida  does 
not  exhibit  those  marked  variations  of  structure  which 
are  seen  in  most  orders.  While,  however,  the  general 
features  remain  essentially  the  same,  the  details  vary 
according  to  the  habits  of  the  different  families.  One  of 
the  oldest  fossil  spiders,  Arthrolycosa  antiqua  Harger  (PL 
908),  while  possessing  the  form  and  the  appendages  of 
most  Arachnida.  yet  apparently  has  certain  other  struc- 
tural features  which  ally  it  with  the  more  generalized  spi- 
ders of  the  present  day,  such  as  Eurypelma  ( =  Mygale) 
(No.  909,  9  ;  No.  910,  £). 

The  position  and  character  ,of  the  mandibles  in  this 
ancient  spider  (PL  908)  seem  to  indicate  that  these 
organs  moved  vertically  like  the  mandibles  of  the  hairy 
Eurypelma.  The  four  pairs  of  walking-feet  are  also 
similar  to  those  of  Eurypelma,  and  altogether  it  is  most 
probable  that  both  genera  belong  to  the  same  suborder, 
the  Tetrapneumones,  which  has  four  air  sacs'  like  the 
scorpions  and  only  four  spinnerets,  two  of  which  are 
long  and  bent  up  behind  the  abdomen.  These  organs 
are  not  so  useful  in  these  hairy  spiders  as  in  some  of  the 
more  specialized  Arachnida,  since  they  do  not  spin  elab- 
orate webs  for  catching  their  prey,  but  live  in  nests  made 
in  the  ground.  One  genus  (Cteniza)  of  this  group  makes 
the  ingenious  trap-door  nest  (No.  911).  These  nests  are 
usually  constructed  in  the  moist  earth  which  afterwards 
hardens  ;  they  are  lined  with  soft  silk  from  the  spinner- 
ets, and  the  door  is  skillfully  hinged,  fitting  snugly  into 
the  opening.  By  means  of  the  claws  on  the  feet  or  the 
fangs  of  the  mandibles1  the  trap-door  (see  No.  911)  is 
raised  and  the  spider  backs  down  the  tube,  the  door  clos- 

1  McCook  says  "apparently  the  fangs."    Amer.  Spiders  and  their 
Spinning-work,  III,  1893,  p.  30. 


METAZOA ARACHNOZOA.  369 

ing  upon  her.  When  within  the  nest  the  occupant  is  safe, 
for  the  external  appearance  of  the  door  is  like  the  sur- 
rounding surface.  "  If  the  bank  is  bare,"  says  McCook, 
"  the  top  of  the  door  is  also  bare ;  if  the  bank  is  covered 
with  lichens  the  spider  cuts  a  crop  of  minute  lichens  and 
glues  them  with  nice  judgment  to  the  outside  of  her  door, 
thus  disguising  the  entrance." 

It  is  an  interesting  fact  that  the  habit  of  nest-building 
has  become  so  strongly  fixed  in  the  organization  of  the 
adult  that  it  is  inherited  at  an  extremely  early  age  by  the 
offspring.  "That  so  young  and  weak  a  creature,"  says 
McCook,  "should  be  able  to  excavate  a  tube  in  the  earth 
many  times  its  own  length  and  know  how  to  make  a  per- 
fect miniature  of  the  nests  of  its  parents,  seems  to  be  a 
fact  which  has  scarcely  a  parallel  in  nature."  * 

The  difference  in  the  sexes  is  not  so  marked  in  these 
more  generalized  spiders  (compare  No.  909,  9  ,  with  No. 
910,  £  )  as  in  the  more  specialized  forms  (see  Nos.  913, 
915,  916,  919,  921,  922),  in  which  the  male  is  extremely 
reduced  in  size. 

The  brilliantly  colored,  unnamed  spider  (No.  912)  is 
allied  to  Eurypelma.  Its  abdomen  is  covered  with  a 
thick  coating  of  hair  and  two  long,  light  colored  spinner 
ets  extend  outward  while  the  other  pair  is  short. 

Among  the  spinners  the  tube-weavers  are  represented 
in  the  Collection  by  the  common  grass  spider,  Agalena 
naevia  Walck.  (No.  913,  9,  £),  and  the  orb-weavers  by 
five  genera  of  the  Epeiridae  :  Nephila,  Epeira,  Argiope, 
Mahadeva,  and  Acrosoma. 

It  is  the  grass  species,  Agalena,  that  makes  the  hori- 
zontal webs  (PI.  914)  on  grass  that  are  brought  into  view 
by  the  sparkling  dew  of  the  early  summer  mornings,  but 
which  in  reality  are  on  the  grass  all  the  time,  often  re- 
maining for  months  in  favorable  localities.  PI.  914 
shows  the  tube  at  one  side  of  the  web  where  the  spider 

1  Loc.  ctt.,  II,  1890,  p.  251. 


370  SYNOPTIC    COLLECTION. 

stays  and  from  which  the  forward  part  of  its  body  is  put 
out.  The  web  is  so  close  and  tight  that  according  to 
Emerton1  "one  can  hear  the  footsteps  of  the  spider  as 
she  runs  about  on  it." 

When  the  web  is  finished  she  waits  in  the  tube  until  an 
insect  is  caught  in  the  snare  when  she  runs  out,  catches 
her  prey,  and  retires  into  the  tube  to  eat  it. 

Just  as  the  young  Cteniza  knows  how  to  construct  its 
trap-door  nest,  so  the  young  Agalena  possesses  a  knowl- 
edge of  the  art  of  web-making  inherited  from  its  ances- 
tors near  and  remote. 

Nephila  (PI.  915,  N.  plumipes  Koch)  differs  from  the 
other  orb-weavers  in  having  an  abdomen  much  longer 
than  the  cephalothorax.  In  life  this  spider  is  brilliantly 
colored  and  provided  with  hairs  of  a  silvery  luster.  The 
difference  between  the  sexes,  which  is  generally  great,  is 
seen  in  this  genus,  the  male  (fig.  2)  being  about  a  tenth 
as  large  as  the  female  (fig.  i). 

The  common  spider,  Epeira  sdopetaria  Clerck  (=£. 
vulgaris  Hentz),  (No.  916,  9,  $  ;  PI.  917,  figs,  i,  2)  car- 
ries the  art  of  web-making  to  great  perfection.  It  selects 
a  window-frame,  fence,  or  some  other  favorable  locality 
and  spins  a  line  across  the  space  where  the  future  web  is 
to  be.  Then  it  spins  radial  threads  as  seen  in  PI.  918 
from  the  center  to  certain  fixed  points  on  the  circumfer- 
ence. When  this  is  done  it  makes  a  spiral  scaffolding 
from  the  center  to  the  outside,  then  retracing  its  steps,  it 
spins  a  closer  spiral  of  adhesive  threads  (see  PI.  918) 
behind  it  while  it  tears  down  the  scaffolding  in  front  of 
it.  On  approaching  the  center  it  allows  the  scaffolding 
of  non-adhesive  threads  to  remain,2  evidently  because  it 
is  here  at  the  center  that  the  spider  stays  much  of  the 
time.  When  the  prey  is  caught  in  the  web  the  spider 


1  The  Structure  and  Habits  of  Spiders,  1878,  p.  55. 

2  Campbell,  Trans.  Hertfordshire  Nat.  Hist.  Soc.,  I,  part  i,  1880, 
p.  44- 


METAZOA ARACHNOZOA.  371 

runs  down  the  radial  non-adhesive  threads  to  get  it,  or 
when  alarmed  it  hurries  down  a  special  thread,  made  for 
the  purpose,  to  its  nest  (in  the  upper  right  hand  corner  of 
PI.  918.) 

The  characters  of  this  genus  are  typical.  As  in  most 
spiders,  the  small,  flattened  cephalothorax  is  connected 
with  the  large,  plump  abdomen  by  an  extremely  narrow 
waist  (PI.  917,  fig.  i  ;  fig.  2,  a).  The  eyes  in  all  Arach- 
nida  are  single,  and  in  this  species  there  are  eight  (fig.  i) 
of  which  six  are  figured  near  the  front  edge  of  the  cepha- 
lothorax. The  Peckhams1  have  shown  that  different 
species  of  spiders  can  see  from  one  or  two  inches  to 
twelve  inches,  and  in  the  opinion  of  these  investigators 
they  have  the  power  of  distinguishing  colors. 
.  Epeira,  like  all  spiders,  has  no  antennae,  but  according 
to  Emerton,  both  the  palpi  and  first  pair  of  legs  at  times 
perform  the  function  of  these  organs.  The  mandibles 
are  strong,  black  organs  (fig.  2,  d)  which  move  laterally 
and  are  provided  with  sharp  fangs  through  which  the 
poison  flows.  The  only  other  mouth  parts  are  the  two 
maxillae  (fig.  2,<?)  which  bear  the  palpi  that  are  enlarged 
in  the  male  (No.  916,  specimen  on  the  right)  and  used 
as  organs  of  copulation. 

The  long  seven-jointed  legs  (PI.  917,  fig.  2,  b}  are  pro- 
vided with  claws  that  are  admirably  adapted  for  walking 
on  a  web. 

The  abdomen  bears  three  pairs  of  spinnerets  (fig. 
2,  s)  which  represent  as  many  pairs  of  legs.  The  third 
pair  are  short  and  not  distinctly  seen  until  the  other  two 
pairs  are  separated.  Each  of  these  spinnerets  bears 
many  minute  horny  tubes  from  which  the  jets  of  liquid 
matter  issue,  almost  immediately  solidifying,  while  the 
feet  of  the  spider  unite  the  strands  into  a  cord  of  cob- 
web. The  anus  (fig.  2,  n)  is  situated  a  Uttle  behind  the 

JThe  Sense  of  Sight  in  Spiders,  Trans.  Wisconsin  Acad.  Sci. 
Arts  and  Letters,  X,  1894,  p.  249. 


372  SYNOPTIC    COLLECTION. 

posterior  pair  of  spinnerets.  The  genital  opening  (fig. 
2,y)  is  at  the  anterior  end  of  the  abdomen,  and  on  either 
side  of  this  opening  there  is  a  horny  patch  of  skin  which 
marks  the  position  of  the  two  air  sacs  or  lungs  (fig.  2,  /z). 
Besides  these  lungs  the  spider  is  provided  with  air-tubes 
or  tracheae  opening  in  a  single  spiracle,  just  in  front  of 
the  spinnerets  (fig.  2,  k). 

One  of  our  largest  spiders  is  the  brightly  colored  Argi- 
ope  cophinaria  Walck.  (  =  Epeira  riparia  Hentz)  (No.  919, 
9  ,  $ ),  which  is  abundant  in  certain  places  along  our 
coast,  no  less  than  three  hundred  and  forty  having  been 
collected  in  an  hour  at  Beachmont,  Massachusetts. 

This  spider  hangs  out  from  the  middle  of  its  web  and 
being  brightly  colored  is  a  conspicuous  object ;  for  this 
reason  it  would  seem  that  it  would  fall  an  easy  prey  to  its 
enemies.  It  has,  however,  protected  itself  in  a  most 
ingenious  way.  On  either  side  or  in  front  of  its  web  (PI. 
920)  it  spins  many  irregular  threads.  The  spider  has 
such  a  delicate  sense  of  touch  that  if  one  but  lightly 
place  his  finger  on  a  thread,  "she  falls  like  a  shot  to  the 
ground,  where  with  her  back  down,  and  her  legs  drawn 
in  she  is  difficult  to  find,  unless  you  have  followed  the 
drop  with  your  eye.  Or  approach  the  web  without  touch- 
ing it ;  your  shadow,  the  sound  of  your  footstep,  or  per- 
haps the  vibration  of  the  ground  warns  her;  still,  the 
danger  does  not  seem  imminent ;  she  has  time  to  make 
use  of  another  power  —  she  will  render  herself  invisible. 
The  web  begins  to  sway  backward  and  forward ;  the 
rapidity  of  the  motion  increases ;  the  outlines  become 
indistinct,  and  within  a  few  seconds  of  the  first  move- 
ment, spider,  web  and  all  have  vanished  from  sight ! " l 

Another  species  of  Argiope  (No.  921,  A.  argyraspides 
Walck.,  9,  <£)  from  Long  Island  in  Casco  Bay,  Maine, 
is  conspicuous  tor  its  size,  light  color,  and  banded  legs. 


1  Peckham,    Occasional    Papers,    Nat.    Hist.    Soc.    Wisconsin,  I, 
1898,  pp.  72,  73. 


METAZOA ARACHNOZOA.  373 

Peculiar  modifications  in  the  shape  of  the  body  are  seen 
in  Mahadeva  vernicosa  Hentz  (No.  922,  9  ,  $  ;  PI.  923, 
fig.  i,  9  ;  fig.  2,  <£).  The  abdomen  is  triangular  and 
nearly  as  wide  in  front  as  the  body  is  long.  The  male 
(No.  922,  specimen  on  the  right;  PI.  923,  fig.  2)  has 
extremely  long  fore  legs,  while  the  second  pair  are  pro- 
vided with  remarkable  clasping  spines. 

Acrosoma  (No.  924,  A.  gracile  Walck.,  dorsal  and  side 
views;  also  PI.  925,  figs.  1-4)  has  a  very  different  form 
from  the  others  already  described.  The  cephalothorax  of 
the  female  (No.  924 ;  PI.  925,  fig.  i,  upper  side)  is  small, 
glossy,  and  dark  colored,  while  the  abdomen  is  broad  at 
the  posterior  end  and  provided  with  spikes  on  each  side 
(fig.  i  ;  fig.' 2,  lower  side,  x  4).  Jt  is  flattened  above 
and  is  light  colored  (fig.  i),  while  the  ventral  side  is 
darker  colored  and  the  spinnerets  extend  forward  in  a 
conical  peak  to  the  middle  of  the  abdomen  (fig.  i  ;  fig.  3, 
side  view  of  the  same,  x  4),  giving  a  most  peculiar  ap- 
pearance to  the  animal.  The  male  (fig.  4,  x  4)  is  very 
much  smaller  than  the  female  (fig.  2,  x  4)  and  is  distin- 
guished by  the  enlarged  palpal  organs. 

Among  the  more  differentiated  spiders  are  the  runners 
like  the  Lycosidae  and  the  leapers  or  Attidae.  They 
have  a  well  developed  cephalothorax  and  keen  organs  of 
sense.  According  to  the  observations  of  the  Peckhams,1 
the  sense  of  sight  is  especially  strong  in  these  families. 

The  runners,  like  Lycosa  (No.  926)  have  long  hind 
legs,  enabling  their  possessors  to  run  swiftly  while  catch- 
ing their  prey.  The  leapers,  like  Phidippus  galathea 
Walck.,  (=  Attus  audax  Hentz)  (No.  927),  have  short 
legs,  the  first  pair  being  the  stoutest.  The  Lycosidae 
have  three  pairs  of  spinnerets,  like  the  orb-weavers. 
Though  they  do  not  spin  webs  for  catching  prey,  they 
construct  homes  for  themselves  in  the  earth,  line  them 
with  silk,  and  over  them  erect  a  chimney. 


1  The  Sense  of  Sight  in    Spiders,  Trans.  Wisconsin  Acad.  Sci., 
Arts  and  Letters,  X,  1894. 


374  SYNOPTIC    COLLECTION. 

These  spiders,  notably  the  Lycosidae,  take  especial 
care  of  their  young.  Not  only  are  the  eggs  protected  by 
a  cocoon,  as  in  most  spiders,  but  the  mother  Lycosa  car- 
ries the  cocoon  about  with  her  until  the  larvae  are 
hatched.  Rather  than  desert  it,  she  will  carry  or  draw  it 
after  her,  and  will  defend  it  to  the  last  (Campbell). 
McCook  l  records  an  instance  of  maternal  ingenuity  on 
the  part  of  one  species  of  Lycosa  (Z.  tigrina)  whereby  a 
nest  was  provided  with  "a  window."  The  builder  had  a 
cocoon  attached  to  her  spinnerets  and  she  would  put  her- 
self in  a  position  to  let  it  lie  against  the  window  where  it 
received  the  warm  rays  of  the  sun.  For  three  weeks  her 
daily  occupation  was  holding  her  egg-sac  in  the  sunlight. 

When  the  eggs  hatch,  the  larvae  moult  their  first  skin 
within  the  cocoon.  Sometimes  a  second  skin  is  shed  be- 
fore the  larvae  get  on  their  mother's  back.  She  carries 
them  until  the  third  and  sometimes  the  fourth  skin  is 
moulted,  when  they  are  able  to  take  care  of  themselves. 

Among  the  Saltigrades  is  the  interesting  Synageks 
picata  Hentz  (PI.  928),  which  strikingly  resembles  an  ant. 
This  is  probably  a  case  of  protective  resemblance.  The 
first  pair  of  legs  extend  forward  and  resemble  antennae 
so  that  only  three  pairs  extend  outwardly,  although  there 
are  four  pairs  in  all,  —  the  characteristic  number  among 
spiders. 

The  Arachnida  which  are  most  specialized  by  the 
reduction  of  some  parts  and  the  modification  of  others 
are  the  mites.  These  are  represented  by  several  species. 
Atax  (No.  929,  A.  bonzi,  fig.  i,  ventral  view  of  larva)  is  a 
water  mite,  living  in  the  gills  of  Unio.  The  larva  in  this 
case  has  the  same  number  of  feet  as  the  adult  (fig.  2, 
dorsal  view).  Tetranychus  (No.  930,  T.  telarius ;  fig.  i, 
larva;  fig.  2,  adult)  is  found  on  plants  in  greenhouses, 
while  another  genus,  Tyroglyphus,  includes  the  cheese 
and  sugar  mites.  The  latter  have  scissors-like  mandibles 

1  Amer.  Spiders  and  their  Spinning-work,  III,  1893,  p.  25. 


METAZOA ARACHNOZOA.  375 

and  the  feet  are  provided  with  claws  and  suckers.  Tyro- 
glyphus  setiferus  (PI.  931)  has  long  bristles  or  setae 
extending  from  the  body.  This  figure  also  exhibits  the 
digestive  system,  though  the  anus  is  not  seen,  as  it  is  sit- 
uated ventrally  near  the  posterior  end  of  the  body.  Four 
eggs  are  seen  on  the  ventral  side  (PI.  931). 

Another  more  specialized  form  is  the  itch  mite,  Sar- 
coptes  scabiei  Latr.  (PI.  932,  figs.  1-4).  The  larva  (fig.  i) 
has  a  nearly  circular  body  in  which  cephalothorax  and 
abdomen  are  indistinguishable.  It  is  provided  with 
needle-like  mandibles,  and,  like  the  larvae  of  most  mites, 
with  three  pairs  of  feet,  the  two  forward  pairs  having 
suckers  for  clinging  to  the  host  even  at  this  early  age. 

The  female  (fig.  2,  upper  side;  fig.  3,  lower  side)  is 
essentially  like  the  larva  in  form,  but  has  four  pairs  of 
feet ;  the  two  forward  pairs  having  large  suckers  (figs. 
2,  3)  and  the  two  hinder  pairs  long  bristles.  The  male 
(fig.  4)  is  smaller  than  the  female,  but  like  her  has  four 
pairs  of  legs ;  each  of  the  third  pair  ends  in  a  sucker,  and 
each  of  the  fourth  pair  in  a  bristle. 

The  members  of  one  family  of  mites,  the  Ixodidae,  are 
usually  called  ticks.  One  of  the  common  examples  of 
this  group  is  the  cattle  tick,  Boophilus  bovis  Riley  (PI. 
933,  figs.  1-6).  The  six-footed  larva  (fig.  i,  greatly 
enlarged)  looks  like  a  minute  seed,  having  a  body  in 
which  the  cephalothorax  and  abdomen  are  united  in  one 
mass.  These  larvae  fasten  themselves  on  cattle  and 
develop  into  the  adult  (fig.  2,9,  natural  size  when  gorged 
with  food  :  fig.  3,  9  ,  enlarged  ;  fig.  4,  £).  The  mandi- 
bles (fig.  5)  are  fitted  for  piercing  the  hide,  and  as  their 
hooks  extend  backward  they  enable  the  tick  to  hold 
tightly  while  sucking  the  blood  of  its  victim.  The  feet 
of  the  tick  are  also  adapted  for  clinging  to  its  host,  the 
hind  feet  (fig.  6)  having  two  claws  and  a  sucking  disc  as 
well  as  a  double  spur. 

Boophilus  illustrates  the  law  of  acceleration  in  develop- 
ment since  it  is  able  to  lay  eggs  any  time  after  it  is  half 


376  SYNOPTIC    COLLECTION. 

grown,1  and  a  mite,  Sphaerogyna  ventricosa,  carries  the 
process  still  further  if  it  is  true  that  it  produces  sexually 
mature  animals  which  are  fertilized  as  soon  as  born.2 

It  is  probable  that  the  parasitic  habit  of  the  larva  of 
many  species  of  mites  tends  to  reduce  the  number  of  legs 
in  this  stage,  and  this  view  finds  confirmation  in  the  fact 
that  some  of  the  mites  of  the  family  Oribatidae  which  are 
terrestrial,  living  in  moss,  under  stones,  and  the  like,  are 
said  to  have  four  pairs  of  legs  when  hatched.3 

While  most  mites  have  four  pairs  of  legs  in  the  adult 
stage,  it  is  interesting  to  note  that  the  gall-making  species, 
Phytoptus  pyri  Scheuten  (PI.  934,  fig.  i),  which  bores 
into  leaves  and  lives  in  the  cavities  or  galls  that  it  makes, 
has  only  two  pairs  of  these  organs. 

Among  the  mites,  the  sea-spiders  or  Pycnogonida  may 
be  placed,  though  there  is  a  diversity  of  opinion  among 
naturalists  in  regard  to  their  true  position.  Morgan4  has 
shown,  however,  that  the  younger  stages  of  the  Pycnogo- 
nids  tend  to  prove  a  relationship  with  the  Arachnida. 
This  group  is  represented  in  the  Collection  by  Phoxichi- 
lidium  (No.  935,  upper  specimens  on  the  tablet)  and  Pyc- 
nogonum  (No.  935,  lower  specimens).  In  these  forms 
the  abdomen  is  a  mere  vestige,  while  the  anterior  part  of 
the  body  extends  forward  into  a  proboscis  which  is  used 
for  sucking.  In  reality,  there  is  scarcely  any  body,  the 
animal  being  almost  wholly  made  up  of  legs  into  which 
extend,  apparently  of  necessity,  some  of  the  internal 
organs.  The  more  typical  members  of  the  group,  like 
Nymphon  stromi  Kroyer  (PI.  936,  fig.  i,  <£)  have  besides 
the  proboscis  a  pair  of  clawed  appendages  (fig.  i)  which 
are  considered  antennae  by  Wilson  and  mandibles  by 


l.  24,  Texas  Agric.  Exper.  Sta.,  1892,  p.  242. 

2  See  Shipley,  Zool.  of  the  Invert.,  1893,  p.  420. 

3  See  Kingsley,  Stand.  Nat.  Hist.,  II,  1884,  p.  102. 

4  Johns    Hopkins  Univ.,    Stud.  Biol.  Lab.,  V,  no.    i,    1891,   pp. 
25-33- 


METAZOA ARACHNOZOA.  377 

others ;  these  are  sometimes  followed  by  a  pair  of  palpi 
(fig.  i).  Back  of  these  appendages  there  is  a  pair  of  ac- 
cessory legs  in  both  the  male  and  the  female.  Singularly 
enough  the  work  usually  done  by  the  female  of  carrying 
and  thereby  protecting  the  eggs  is  performed  in  Pycno- 
gonids  with  a  single  exception  by  the  male  (Kingsley).  • 

There  are  four  pairs  of  walking-legs 1  which  are  ex- 
tremely long  and  hooked  at  their  ends.  Phoxichilidium 
has,  in  common  with  Nymphon,  the  antennae  and  acces- 
sory legs. 

Pycnogonum  (No.  935  ;  PI.  936,  fig.  2),  on  the  other 
hand,  is  without  antennae  in  the  adult  stage,  though  the 
larva  possesses  them.  The  legs  of  the  male  for  carrying 
the  eggs  are  very  small  (see  PI.  936,  fig.  2),  while  they 
are  wanting  altogether  in  the  female.  This  genus  has 
much  stouter  and  shorter  walking-legs  than  Nymphon, 
and  they  end  in  larger  claws. 

The  Pycnogonids  differ  from  the  spiders  in  having  no 
tracheae  nor  lung  sacs,  respiration  being  carried  on  by  the 
general  surface  of  the  body. 

One  of  the  puzzling  forms  of  animal  life  is  Linguatula 
(PI.  937  ;  No.  938).  It  has  been  placed  among  the 
Worms,  the  Crustacea,  and  at  present  is  considered  as  a 
near  ally  of  the  mites  and,  therefore,  placed  among  the 
Arachnida.  Its  parasitic  habit  has  completely  disguised 
the  adult,  and  were  it  not  for  the  larva  one  would  be 
wholly  unable  to  classify  it.  This  larva  (PL  937,  fig.  i, 
lower  side;  fig.  2,  upper  side  of  L.  proboscidea  Rud.)  is 
an  internal  parasite.  Its  body  shows  no  separation  into 
cephalothorax  and  abdomen.  The  jaws  are  horny ;  the 
two  pairs  of  jointed  legs  are  similar  in  shape  and  are  pro- 
vided with  hooks.  The  larva  finds  its  way  to  the  liver  or 
the  lungs  of  its  host  —  a  reptile,  the  python,  in  this 
case  —  and  becomes  encysted  (fig.  3  ;  fig.  4,  taken  from 
the  cyst;  fig.  5,  the  same  enlarged). 

1  In  regard  to  the  different  views  held  concerning  the  third  and 
seventh  pairs  of  appendages,  see  Morgan,  loc.  «'/.,  p.  31. 


378  SYNOPTIC  COLLECTION. 

In  the  process  of  growth  the  animal  elongates  (No. 
938)  and  the  body  wall  becomes  constricted,  forming 
ridges  or  raised  rings  throughout  nearly  its  whole  length. 
The  mouth  parts  are  represented  by  two  pairs  of  horny 
hooks  only,  on  either  side  of  the  mouth  (No.  938 ;  PI. 
937?  %•  5)i  ar>d  the  feet  have  wholly  disappeared.  In 
addition  to  this  loss  of  external  organs,  Linguatula  is 
without  a  heart,  tracheae,  or  lung  sacs,  respiration  being 
effected  by  the  skin. 

The  life  history  of  Linguatula  proboscidea  Rud.,  is  not 
so  well  known  as  that  of  L.  taenioides  Rud.  The  mature 
female  of  the  latter  species  is  found  in  the  nasal  passages 
of  the  dog  where  the  eggs  are  laid.  These  are  expelled 
by  sneezing  and  are  scattered  on  the  grass.  The  latter  is 
eaten  by  some  herbivorous  animal.  The  embryo  develops 
into  the  four-footed  larva  which  has  mouth  parts  adapted 
for  boring.  By  means  of  these  the  larva  finds  its  way  to 
the  liver  or  lungs  of  its  host  and  there  becomes  encysted. 
When  the  herbivorous  animal  is  eaten  by  a  dog  the  cyst 
is  ruptured  and  the  mature  female  makes  its  way  to  the 
nasal  passages,  when  the  process  is  repeated. 


MALACOPODA. 


Section  14  (in  part). 

One  of  the  most  interesting  animals  is  Peripatys  (No. 
939,  P.  edwardsi  Blanch,  or  P.  trinidadensis  ;  PI.  940, 
figs.  1-4,  P.  capensis,  drawn  from  life,  life  size).  It  is  a 
synthetic  form,  combining  characters  of  Mollusca,  Anne- 
lids and  Malaeopods.  It  is  '''an  animal  of  striking 
beauty/7  says  Adam  Sedgwick.1  "The  exquisite  sensi- 

1  Stud.  Morphological  Lab.,  Univ.  Cambridge,  IV,  part  2,  1888, 
P-  155- 


METAZOA MALACOPODA.  379 

tiveness  and  constantly  changing  form  of  the  antennae, 
the  well-rounded  and  plump  body,  the  eyes  set  like  small 
diamonds  on  the  sides  of  the  head,  the  delicate  feet,  and, 
above  all,  the  rich  coloring  and  velvety  texture  of  the 
skin,  combine  to  give  these  animals  an  aspect  of  quite 
exceptional  beauty.  Of  all  the  species  which  I  have 
seen  alive,  the  most  beautiful  are  the  dark  green  individ- 
uals of  Capensis,  and  the  species  which  I  have  called 
Balfouri.  These  animals,  so  far  as  skin  is  concerned, 

are  not  surpassed  in  the  animal  kingdom I  shall 

never  forget  my  astonishment  and  delight  when  on  tear- 
ing away  the  bark  of  a  rotten  tree-stump  in  the  forest  on 
Table  Mountain,  I  first  came  upon  one  of  these  animals 
in  its  natural  haunts." 

Peripatus  has  been  considered  rare,  but,  according  to 
J.  E.  Duerden,1  it  has  been  found  in  great  numbers  on 
the  eastern  side  of  the  Island  of  Jamaica.  It  is  cylindri- 
cal in  form  (No.  939;  PL  940,  fig.  i).  The  color  in 
P.  capensis  varies  from  dark  green  to  bluish  gray,  with  a 
light  band  at  the  bases  of  the  legs  which  extends  the 
whole  length  of  the  body  (fig.  i).  There  are  no  distinct 
segments  but  the  skin  is  thrown  into  numerous  fine  ridges 
that  bear  papillae,  each  one  of  which  is  provided  with  a 
tiny  spine  (fig.  2). 

The  forward  part  of  the  body  is  not  differentiated  into 
a  distinct  head,  although  it  bears  the  eyes,  the  jointed 
antennae,  and  the  mouth  parts  (fig.  2).  The  eyes  con- 
sist of  a  group  of  ocelli  and  are  therefore  simple  and 
unstalked.  The  mouth  parts  consist  of  a  pair  of  mandi- 
bles or  jaws,  colored  reddish  yellow  in  fig.  2,  placed  on 
either  side  of  the  opening  ;  each  of  these  jaws  has  a  pair 
of  sickle-shaped  claws  at  its  free  extremity.  On  the  up- 
per or  dorsal  side  of  the  mouth  is  the  tongue,  seen  in  fig. 
2,  extending  downward  between  the  jaws.  On  either 
side  of  the  mouth,  near  the  base  of  the  antennae,  are  the 
oral  papillae. 

1  Nature,  LXIII,  March  7,  1901. 


380  SYNOPTIC  COLLECTION. 

In  speaking  of  segments  Mr.  Scudder  says,1  "The 
entire  body  [of  Peripatus]  is  of  a  leathery  texture  with  no 

external  signs  of  segments The  same  is  true  when 

the  internal  structure  of  the  body  is  examined,  for  neither 
in  the  disposition  of  the  muscles  nor  of  the  tracheal  ap- 
paratus does  it  appear  that  one  could  judge  whether  a 
pair  of  legs  represented  one  or  more  segments  of  the 
body  ;  even  in  the  nervous  system  it  is  only  indicated 
by  a  small  ganglionic  swelling  next  each  pair  of  legs. 
The  tracheae  are  like  extended  cutaneous  glands,  inde- 
pendent of  one  another  and  scattered  over  the  body,  and 
the  longitudinal  muscles  show  no  segmental  breaks." 
This  weakness  of  segmental  divisions  is  evidence  of  spe- 
cialization by  reduction,  and  we  therefore  place  Peripatus 
among  those  forms  that  have  become  more  or  less  modi- 
fied from  the  ancestral  type  by  the  suppression  of  certain 
characters,  such  as  distinct  segmentation  of  the  body 
and  distinctly  jointed  legs.  We  have  already  pointed 
out  many  cases,  especially  among  parasites,  where  there 
is  a  marked  weakness  in  segmentation. 

Peripatus  when  disturbed  secretes  a  quantity  of  slime, 
the  slime  glands  opening  at  the  end  of  the  oral  papillae. 
The  mouth  is  encircled  by  a  lip  which  is  raised  into 
papillae,  and  these  adhere  to  the  food  while  the  jaws 
probably  tear  it  in  pieces. 

The  different  species  of  Peripatus  are  determined  in 
part  by  the  number  of  paired  walking-legs,  Peripatus 
capensis  (PI.  940,  fig.  i  ;  fig.  3,  leg  enlarged)  having 
seventeen  pairs  and  Peripatus  edwardsi  (No.  939)  having 
from  twenty-nine  to  thirty-four  pairs.  These  legs  are 
similar  in  function  and  therefore  in  structure.  They  are 
obscurely  jointed ; 2  and  since  Peripatus  lives  in  damp 

1  Mem.  Boston  Soc.  Nat.  Hist.,  Ill,  no.  9,  1884,  p.  287. 

2  Scudder,   Amer.  Journ.   Sci.,    (3),  XXIV,   1882,  p.   166,   says, 
legs  "obscurely   jointed,   the  joints  being  perceptible  only  at  the 
extreme  tip  and  on  the  apical  half  of  the  inner  side." 


METAZOA MALACOPODA.  381 

places,  preeminently  under  the  bark  of  decaying  stumps, 
the  legs  are  soft  and  fleshy ;  hence  the  name  of  Mal- 
acopoda.  The  leg  proper  is  provided  with  many  rings  of 
papillae  and  at  its  lower  end  are  three  pads.  The  foot 
carries  two  claws  and  several  papillae  (PI.  940,  fig.  3). 
At  the  bases  of  the  feet  on  the  ventral  surface  the  paired 
excretory  organs  or  nephridia  open.  The  presence  of 
these  organs  in  Peripatus  recalls  the  similar  organs  we 
have  already  found  in  Worms. 

Peripatus  breathes  by  means  of  tracheae  which,  how- 
ever, do  not  appear  until  the  animal  is  hatched.1  The 
spiracles  are  scattered  irregularly  over  the  body,  each 
spiracle  (PI.  940,  fig.  4)  leading  into  a  tracheal  pit 
which  spreads  out  into  a  bundle  of  tracheal  branches 
(see  fig.  4)  that  never  unite. 

Peripatus  is  viviparous,  the  period  of  gestation  cover- 
ing thirteen  months ;  this  being  the  case,  a  comparatively 
small  number  of  individuals  is  produced  and  these  re- 
semble the  parent  at  birth  excepting  in  color.  While  the 
adults  of  P.  capensis  are  of  a  rich  green,  the  little  ones 
ar'e  nearly  white  with  green  antennae.  According  to 
Steel,  the  animals  cast  their  skins  like  many  insect 
larvae,  and  the  cast  skins  are  generally  worked  over  with 
the  jaws  and  finally  swallowed. 

The  general  more  or  less  slug-like  appearance  and  the 
possession  of  a  nervous  system  similar  to  that  of  Chiton 
caused  some  naturalists  to  place  Peripatus  among  the 
Mollusca.  Its  closer  resemblance  in  form  to  the  Worms, 
the  possession  of  paired  appendages  along  the  whole 
length  of  the  body,  and  still  more  the  presence  of  rows 
of  paired  nephridia  caused  naturalists  later  to  place 
Peripatus  in  the  subkingdom  of  Vermes. 

The  discovery  of  true  tracheae  and  spiracles,  the  pos- 
session of  jointed  antennae  and  legs,  the  existence  of 
appendages  modified  as  jaws,  and  of  certain  important 

1  Packard,  Text-book  of  Ent.,  1898,  p.  15. 


38*2  SYNOPTIC    COLLECTION. 

resemblances  in  internal  structure,  place  Peripatus  to-day 
among  the  articulated  animals  with  jointed  appendages. 

Its  worm-like  affinities  together  with  its  scattered  spira- 
cles and  the  single  pair  of  jaws  seem  to  take  Peripatus 
from  the  Myriapods — probably  its  nearest  allies — and 
to  place  it  in  a  class  by  itself. 

It  may  be  that  Peripatus  is  the  survivor  of  a  primitive 
type  which,  however,  has  lost  some  of  its  primitive  char- 
acters, and  become  more  or  less  specialized  by  the  suppres- 
sion of  parts.  The  loss  of  segmentation  and  the  obscure 
jointing  of  the  legs  would  point  to  this  conclusion,  while 
the  power  possessed  by  Peripatus  of  bringing  forth  its 
young  alive  is  an  indication  of  specialization  of  structure. 
The  retention  of  paired  nephridia  suggests  its  possible 
remote  origin  from  some  worm-like  form,  while  the  pos- 
session of  tracheae  proves  that  it  is  far  removed  from  the 
Worms  and  is  doubtless  near  the  Myriapods  and  Insects. 


MYRIAPODA. 


Section   14  (in  part). 

"The  relations  of  ancient  to  modern  forms  of  life," 
says  Scudder,1  "prove  far  more  important  and  interesting 
in  the  myriopoda  than  in  either  the  arachnida  or  the 
hexapoda." 

This  eminent  authority  points  out  that  the  embryology 
of  living  forms  of  Myriapods  is  inadequate  to  explain  the 
origin  of  the  complex  structure  of  the  segments,  and  that 
we  must  look  to  the  palaeontologic  record  for  light  on  this 

'The  Geological  History  of  Myriopods  and  Arachnids,  Psyche, 
IV,  Jan.-March,  1885,  p.  245  ;  see  also  Bull.  U.  S.  Geol.  Surv.,  no. 
31,  1886. 


METAZOA MYRIAPODA.  383 

puzzling  problem.  Here  we  find  forms  in  which  simple 
distinct  body  segments  without  any  trace  of  subdivisions 
follow  one  another,  each  segment  bearing  one  pair  of 
jointed  appendages  (PI.  941,  fig.  i,  Palaeocampa  anthrax 
Meek  and  Worthen).  The  boundaries  of  these  segments 
can  be  determined,  as  each  is  made  up  of  a  single  dorsal 
and  a  single  ventral  plate.  The  number  of  segments  is 
small  and  each  segment  bears  a  pair  of  jointed  legs  which 
are  similar  in  structure.  On  the  upper  side  are  tubercles 
which  carry  clusters  of  slender  needles  (see  PI.  941), 
probably  used  as  means  of  defence.  The  head  of  Palae- 
ocampa is  small  but  distinct  and  composed  apparently  of 
only  one  segment. 

The  Chilopoda  of  to-day  probably  descended  from 
Palaeocampa  of  forms  similar  to  it,  but  these  Myriapods 
are  more  specialized  in  certain  important  features  than 
the  Diplopoda,  another  group  of  living  Myriapods,  which 
in  all  probability  descended  from  Archipolypoda  described 
by  Scudder. 

It  may  be  that  future  investigations  into  the  pre-Cam- 
brian  or  the  early  Palaeozoic  rocks  will  bring  to  light  the 
common  ancestor  of  the  Palaeocampa-like  forms,  and  of 
the  Archipolypoda. 

The  segments  of  the  Archipolypoda  are  composed  of 
one  dorsal  and  two  ventral  plates,  but  in  some  of  the 
types  the  dorsal  plate  is  distinctly  seen  to  be  made  of  two 
plates,  which  indicates  that  one  apparent  segment  is  in 
reality  composed  of  two  segments. 

The  Diplopoda,  embracing  the  Millipeds,  of  which 
Jtilus  (No.  942)  is  a  good  example,  have  a  distinct  head 
and  a  plump  cylindrical  body  (which  is  not  divided  into 
thoracic  and  abdominal  regions).  A  dorsal  view  (No.  942, 
specimen  on  the  right),  exhibits  a  succession  of  similar 
segments  of  nearly  equal  size  extending  from  one  end  of 
the  body  to  the  other,  while  a  side  view  shows  the  unusual 
thickness  of  the  body  and  the  small  size  and  great  num- 
ber of  jointed,  single-clawed  legs  fastened  near  the 
median  line  of  the  ventral  surface. 


384  SYNOPTIC    COLLECTION. 

The  preparation  of  Julus  (No.  942,  specimen  on  the 
left),  gives  the  ventral  view  and  exhibits  the  segments 
separated  from  one  another.  Most  of  these  segments 
have  two  ventral  plates  instead  of  one  apparent  plate  as  in 
the  dorsal  view.  These  ventral  plates  are  extremely  small 
and  so  narrow  that  the  legs  which  are  fastened  to  them 
are  crowded  closely  together. 

It  is  seen  that  the  three  complete  anterior  segments 
(which  are  probably  thoracic)  carry  one  pair  of  legs,  while 
the  remaining  segments  which  are  abdominal,  excepting 
the  first  (the  appendages  of  which  are  modified  for  repro- 
ductive purposes),  and  last,  carry  two  pairs  of  these 
appendages. 

The  light  thrown  on  the  structure  of  Myriapods  by 
Palaeocampa  and  Archipolypoda  enables  one  to  see  that 
each  apparent  abdominal  segment  of  the  Diplopoda 
is  most  probably  made  of  two  segments,  the  dorsal  plates 
of  which  have  become  fused.  Furthermore,  the  two  ventral 
plates  of  each  thoracic  segment  have  likewise  fused  into 
one  plate,  and  at  the  same  time  one  pair  of  legs  has  dis- 
appeared. The  present  condition  of  these  segments  is 
therefore  not  primitive  but  rather  secondary  and  special- 
ized. 

The  head  of  Julus  is  free,  as  we  have  said,  but  is  so 
bent  down  as  to  be  concealed  under  the  body  in  a  dorsal 
view.  It  bears  a  cluster  of  ocelli  on  each  side,  one  pair 
of  jointed  antennae,  a  labrum  or  upper  lip,  a  pair  of 
mandibles,  and  one  pair  of  maxillae.  In  the  preparation 
the  sternal  plate  of  one  of  the  cephalic  segments  is  seen. 

The  Julidae  breathe  by  means  of  tracheae  which  do  not 
arise  until  the  animal  is  hatched  (Packard).  The  openings 
of  spiracles  occur  on  each  of  the  ventral  plates.  The 
tracheae  are  in  the  form  of  tufts  of  tubes  which  never  join. 

The  Diplopoda  leave  the  egg  in  a  very  immature  con- 
dition when  only  three  pairs  of  legs  are  formed.  These 
are  small,  partially  developed,  and  are  not  fastened  to 
consecutive  segments,  one  segment  being  skipped. 


METAZOA MYRIAPODA.  385 

A  metamorphosis  is  correlated  with  this  immaturity,  as 
we  have  seen  in  other  groups  of  the  animal  kingdom. 
The  larval  stage  seems  to  be  adaptive  and  therefore  of 
comparatively  little  phylogenetic  value.  In  time,  the 
thoracic  legs  become  fully  developed  and  the  abdominal 
legs  grow  out  until  finally  the  adult  stage  is  reached. 

The  Chilopoda  or  Centipedes  and  the  like  are  repre- 
sented by  Scolopendra  (No.  943).  They  have  a  de- 
pressed body  consisting  of  fewer  segments  than  are 
found  in  the  Diplopoda.  Each  apparent  segment  bears 
one  pair  of  single-clawed  legs.  These  appendages  are 
on  the  sides  so  that  they  are  widely  separated. 

It  is  probable  that  each  segment  in  the  Chilopods  was 
originally  two  segments,  one  of  which  with  its  pair  of  legs 
became  atrophied.  This  condition  is  farther  removed 
from  the  primitive  state  as  seen  in  Palaeocampa  than  the 
condition  of  the  Diplopods,  and  therefore  the  Chilopods 
may  be  considered  the  more  specialized.  There  is  a  dif- 
ference of  opinion  in  regard  to  the  mouth  parts  of  Chilo- 
pods, some  maintaining  that  there  are  three  pairs  and 
others  that  there  are  four  pairs.  The  former  consider 
that  the  first  pair  of  legs  are  modified  into  poison  fangs, 
while  the  latter  consider  them  as  mouth  organs. 

The  breathing  organs  in  the  Chilopods  are  more  spe- 
cialized than  in  the  Diplopods.  They  consist  of  tubes 
which  unite  to  form  long  tracheal  trunks  that  run  nearly 
the  whole  length  of  the  body.  The  number  of  spiracles 
varies,  but  they  generally  open  on  alternate  segments. 

The  Chilopods  do  not  leave  the  egg  in  an  immature 
condition,  like  the  Diplopods,  but  this  is  passed  within 
the  egg,  and  the  animal  when  hatched  is  usually  fully 
formed  with  all  the  legs  developed.  There  is  accordingly 
no  metamorphosis,  the  development  being  accelerated. 


386  SYNOPTIC    COLLECTION. 


SYMPHYLA. 

The  Symphyla  is  represented  by  the  interesting  little 
Scolopendrella  (PI.  944,  fig  i,  enlarged;  natural  size  indi- 
cated by  vertical  line)  which  Ryder  considers  may  be  the 
last  survivor  of  an  ancestral  form  from  which  insects 
have  descended.  It  is  a  synthetic  type,  combining  char- 
acters of  Myriopods  and  Insects,  the  insectean  features 
predominating. 

The  body  of  Scolopendrella  consists  of  a  limited  num- 
ber of  segments  which  have  the  appearance  of  plates  on 
the  dorsal  side.  The  head  (PI.  944,  fig.  i  ;  fig.  2,  ven- 
tral side,  enlarged)  is  distinct  and  movable.  Twelve  of 
the  segments  bear  jointed  legs  that  terminate  in  two 
claws  instead  of  one,  as  in  the  Myriopods. 

The  antennae  (fig.  2)  are  longer  than  those  of  Myrio- 
pods and  in  structure  are  essentially  different.  They 
resemble  a  series  of  glass  cups  strung  upon  a  delicate 
rod  (Wood-Mason).  There  are  a  pair  of  mandibles  and 
two  pairs  of  maxillae,  the  two  parts  of  the  second  pair 
uniting  to  form  a  lower  lip  or  labium.  The  first  two  pairs 
of  mouth  parts  are  not  fastened  to  the  head  or  skull  by 
a  hinge  joint  as  in  Myriopods  and  most  insects,  but  are 
withdrawn  into  the  head  and  are  buried  in  the  muscles  of 
the  mouth,  so  that  only  the  tips  appear  outside.1 

The  appendages  of  the  last  segment  are  modified  into 
organs  called  cerci  (fig.  2)  ;  at  the  end  of  each  of  these 
is  the  opening  of  the  silk  glands,  the  ducts  of  which  can 
be  seen  in  fig.  2.  At  the  bases  of  the  legs  there  are 
movable  vestigial  ones  (fig.  2)  which  probably  represent 
the  second  pair  of  legs  similar  to  those  found  in  Diplo- 
poda. 

The  internal  organs  are  similar  to  those  of  insects.  A 
small  pair  of  spiracles  are  situated  in  the  front  of  the 

1  Packard,  Amer.  Nat.,  XV,  1881,  p.  701. 


METAZOA SYMPHYLA.  387 

head  near  the  insertion  of'the  antennae,  and  the  tracheae 
(colored  blue  in  fig.  2)  are  simple  air  tubes  without  spiral 
threads,  which  extend  only  a  short  distance  back  into 
the  trunk. 

Besides  these  organs  there  are  nine  or  ten  pairs  of 
ventral  sacs  or  "blood  gills7'  (colored  red  in  fig.  2), 
which  are  situated  within  the  body  near  the  vestigial  feet 
but  which  can  be  turned  outward  as  seen  in  fig.  2. 

Unfortunately,  the  embryology  of  Scolopendrella  is  un- 
known (Packard,  1898),  but  it  is  most  probable  that  the 
larva  has  six  legs  like  the  Diplopods,  and  like  them  de- 
velops more  legs  with  growth. 

The  Symphyla  introduces  us  naturally  to  the  next  and 
last  group  of  invertebrates,  the  Insecta. 


METAZOA  —  INSECTA.  389 

INSECTA. 

Sections  15  and  16. 
Order  i.  —  THYSANURA. 

No  ancestral  form  of  insect  has  been  discovered  among 
the  pre-Cambrian  or  Cambrian  rocks  so  primitive  in  struc- 
ture as  the  living  Campodea  of  the  order  Thysanura. 
This  genus  is  therefore  one  of  the  best  living  representa- 
tives of  that  extinct  ancestral  type  that  gave  rise  to  the 
great  group  of  Insecta.  The  embryology  of  Campodea 
exhibits  no  such  vestiges  of  a  more  specialized  condition 
as  have  been  seen  in  many  genera,  but  the  characters  are 
primitive  and  the  changes  in  structure  are  progressive. 

The  larva  develops  in  a  primitive  way  without  a  meta- 
morphosis or  marked  change  of  any  kind.  It  sheds  its 
skin  only  once  (quoted  by  Packard  after  Grassi)  and  has 
no  resting  period  during  life.  The  external  appearance 
of  the  larva  is  preserved  in  the  adult,  so  slight  is  the 
specialization  attending  growth. 

The  very  small  adult  (PI.  945,  fig.  i,  greatly  enlarged)1 
has  a  long,  somewhat  flattened  (Meinert)  body  divided 
into  segments  that  are  uniform  in  breadth.  A  slight 
differentiation  of  these  segments  has  brought  about  a 
grouping  into  three  regions,  which  is  characteristic  of 
insects,  but  not  found  among  Myriapods.  The  anterior 
region  is  the  head  (fig.  i  ;  PL  946,  fig.  i,  seen  from  below), 
which  is  generally  considered  to  be  made  up  of  an  uncer- 
tain number  of  consolidated  segments.  According  to  the 

1  On  account  of  the  minute  size  of  many  insects,  or  because  they 
are  rare  and  difficult  to  obtain  it  has  been  necessary  to  have  a  large 
number  of  drawings  made.  These  drawings  as  well  as  nearly  all 
in  the  Synoptic  Collection  have  been  made  by  Miss  L.  R.  Martin, 
assistant  in  the  Museum. 


390  SYNOPTIC    COLLECTION. 

observations  of  Folsom,1  however,  the  head  of  insects  is 
composed  of  seven  segments,  each  of  which,  excepting 
the  first  (which  carries  the  eyes),  bears  a  pair  of  append- 
ages. This  naturalist  discusses  the  morphology  of  the 
biting  mouth  parts  of  insects  and  their  nearest  allies,  the 
Crustacea,  Arachnida,  and  Myriapoda,  upon  anatomical 
and  embryological  evidence  derived  from  the  most  primi- 
tive insects.  The  student  in  search  of  the  natural  relation- 
ships of  animals  reads  with  satisfaction  the  following :  "  It 
seems  almost  superfluous  to  insist  that  highly  specialized 
organs  can  be  but  imperfectly  understood  unless  studied 
in  egg  and  larva  as  well  as  imago ;  that  generalized 
types  illuminate  specialized  forms;  and  that  equivalent 
groups  are  linked  together  through  their  more  general- 
ized members ;  yet  too  often  these  accepted  principles 
are  not  applied." 2  Folsom  finds  in  Anurida  maritima 
Guer.,  an  insect  belonging  to  the  Collembola  of  the  primi- 
tive order  Thysanura,  seven  cephalic  segments.  The 
first  or  ocular  segment  carries  the  compound  eyes  which 
this  investigator  homologizes  with  the  compound  eyes 
of  Crustacea.  The  second  segment  bears  the  antennae 
(PI.  947,  fig.  i,  at\  ventral  aspect  of  a  portion  of  the 
germ  band  at  stage  i,  x  480)  homologous  with  the  anten- 
nules  or  first  pair  of  antennae  of  Crustacea  ;  the  third  seg- 
ment a  pair  of  premandibular  appendages  (fig.  i,pr'lmd) 
homologous  with  the  second  pair  of  antennae  of  Crustacea. 
These  mouth  parts  are  rudimentary  and  are  not  even  seen 
when  the  specimen  is  magnified  150  times  (fig.  2).  The 
fourth  segment  bears  the  mandibles  (fig.  i,  md)  homolo- 
gous with  the  same  organs  in  Crustacea;  the  fifth  a  pair 
of  superlinguae  (fig.  3,  j/,  ventral  aspect  of  cephalic 
region  of  germ  band  at  stage  3,  x  480)  homologous  with 
the  first  pair  of  maxillae  in  Crustacea  ;  and  the  sixth  and 
seventh  segments  bear  the  two  pairs  of  maxillae  homol- 

1  Bull.  Mus.  Comp.  Zool.,  XXXVI,  no.  5,  1900. 

2  Folsom,  loc.  cit.,  p.  87. 


METAZOA INSECTA.  391 

ogous  with  the  second  pair  of  maxillae  and  the  first  pair 
of  maxillipeds  in  Crustacea. 

The  view  that  the  head  is  made  up  of  seven  segments 
is  strengthened  by  the  fact  that  seven  ganglia  are  found 
in  the  cephalic  region  of  the  embryo.  Since  the  pre- 
mandibular  and  superlingual  appendages  are  either 
embryonic  or  difficult  to  detect  as  compared  with  the 
mandibles  and  maxillae,  we  will  consider  only  these  latter 
organs  in  this  general  treatment  of  insects. 

The  middle  region  or  thorax  of  Campodea  (see  PI.  945, 
fig.  i)  is  made  of  three  distinct  and  movable  segments 
named  respectively  the  prothorax,  mesothorax,  and  meta- 
thorax.  The  posterior  region  or  abdomen  is  composed 
of  ten  segments,  likewise  distinct  and  freely  movable. 

The  body  is  hairy  and  is  without  scales  or  feathers  ; 
it  extends  longitudinally  and  there  is  little  concentration 
of  parts.  The  junction  of  the  head  with  the  thorax  is  a 
soft  unchitinized  portion  of  the  body  wall  which  forms  a 
functional  neck,  while  the  junction  of  the  thorax  with  the 
abdomen  is  nearly  as  broad  as  the  body  itself,  and  for 
this  reason  the  abdomen  is  said  to  be  sessile. 

The  head  is  without  eyes  according  to  Westwood, 
Meinert,  Lubbock,  and  Oudemans,  while  Nicolet  and 
Grassi  state  that  they  are  present.1 

The  appendages  like  the  body  are  primitive  in  most  of 
their  characteristics.  The  head  is  provided  with  a  pair 
of  long,  hairy  ante'nnae  (Pi.  945,  fig.  i)  and  with  three 
pairs  of  distinct  mouth  parts.  These  latter  organs  are 
the  hollow  mandibles  (PI.  946,  fig.  2,  one  mandible  with 
the  muscles  that  move  it ;  fig.  3,  the  tip  of  the  mandible 
enlarged),  first  pair  of  maxillae  (fig.  4,  showing  the  inner 
lobe,  (rtT),  of  the  right  maxilla,  and  the  outer  lobe,  (e), 
with  its  palpus  (/),  of  the  left  maxilla ;  the  lingua, 

1  On  this  subject  see,  Vire,  Le  Campodea  staphylinus  Westwood, 
et  ses  varietes  cavernicoles ;  Bull.  Mus.  d'  Hist.  Nat.  Paris,  1897, 
no.  3. 


392  SYNOPTIC    COLLECTION. 

hypopharynx,  or  tongue,  (/),  is  seen  in  the  median  line, 
drawn  without  the  supporting  chitinous  frame-work),  and 
the  second  pair  of  maxillae  or  labium  (fig.  i,  /;  palpus 
of  same  enlarged  in  fig.  5).1  Comparatively  speaking, 
these  mouth  parts  are  but  slightly  differentiated,  since 
Campodea  feeds  upon  soft  substances  and  has  no  need 
of  hard,  specialized  mouth  organs.  They  are  set  in  mus- 
cles (some  of  which  are  seen  in  PL  946,  fig.  2)  within 
the  cavity  of  the  skull,  like  those  of  Scolopendrella,  and 
may  be  used  for  either  biting  or  sucking,  although  they 
are  more  allied  to  the  biting  type.  They  are,  in  fact, 
generalized  structures  and  are  probably  similar  to  those 
that  gave  rise  to  the  complicated  organs  for  cutting,  pierc- 
ing, and  sucking  of  the  more  specialized  insects.  This 
view  is  strengthened  by  the  fact  that  the  mouth  parts  of 
Neanura,  one  of  the  Thysanura  of  the  suborder  Collembola, 
have  become  modified  into  suctorial  organs.2 

The  three  pairs  of  legs  attached  to  the  thorax  (PI.  945, 
fig.  i)  are  well  developed  and  similar  in  structure,  since 
they  are  all  used  in  running.  They  are  jointed  and  pro- 
vided at  their  ends  with  two  tiny  hooks  for  taking  hold  of 
objects.  These  legs  are  the  only  appendages  of  the 
thorax  and,  furthermore,  there  are  no  vestiges  or  indica- 
tions of  any  kind  that  the  Campodea  or  the  Thysanura 
ever  possessed  appendages  in  the  form  of  wings.  This 
is  one  of  the  important  reasons  why  the  group  is  entitled 
to  the  position  of  the  most  primitive  order  of  insects. 

According  to  Uzel  the  embryonic  Campodea  has  ten 
distinct  abdominal  segments  of  which  the  first  nine  are 
provided  with  appendages.  In  the  adult  each  of  the  first 

1  According  to  Uzel  these  are  not  the  labial  palpi  but  the  outer 
lobes  of  the  labium      This  author  differs  from  Meinert  in  his  inter- 
pretation of  the  other  parts  of  the  second  pair  of  maxillae  (see  Zool. 
Anz.,  XX,  1897,  p.  234). 

2  Folsom,  The  Anatomy  and  Physiology  of  the  Mouth  Parts  cf 
the    Collembolan,    Orchesella   cincta\^.\    Bull.   Mus.  Comp.  Zool., 
XXXV,  no.  2,  1899,  p.  35. 


METAZOA INSECTA.  393 

seven  segments  of  the  abdomen  has  a  pair  of  similar 
appendages  (PI.  945,  fig.  2),  while  the  last  segment  bears 
a  pair  of  long  appendages  called  cerci  which  resemble 
the  antennae  in  structure. 

The  most  characteristic  system  of  internal  organs  in 
insects  is  the  tracheal  system,  but  it  is  subject  to  great 
variation  owing  to  the  widely  different  physical  conditions 
under  which  insects  live.  According  to  Meinert,  Campo- 
dea  has  three  pairs  of  spiracles,  one  pair  to  each  thoracic 
segment,  while  the  abdomen  is  without  spiracles.  In 
Japyx,  a  closely  allied  genus,  the  abdomen  has  seven 
pairs  of  these  openings.  The  thoracic  spiracles  lead  into 
tracheae  (colored  blue  in  PI.  945,  fig.  2)  which  do  not 
unite  but  simply  form  six  small  independent  subsystems, 
three  on  each  side;  of  these  the  anterior  subsystem  gives 
off  branches  to  the  head,  and  the  posterior  one  to  the  for- 
ward segments  of  the  abdomen  (see  fig.  2). 

Bearing  in  mind  that  the  general  typical  features  of 
Campodea  represent  the  characters  of  the  archetype  of 
the  class  Insecta,-we  pass  to  some  of  its  near  allies. 

Lepisma  saccharina  Linn.,  or  the  "  silver  witch  "  (No. 
948  ;  PL  949,  x  4,  drawn  from  life),  has  a  more  flattened 
body  than  Campodea  and  in  this  particular  respect  it  is 
probably  nearer  the  ancestral  form.  Its  body  is  not  only 
provided  with  hairs  like  that  of  Campodea,  but  many  hairs 
have  become  modified  into  delicate  sculptured  scales 
(No.  950;  PI.  95 1,  fig,  5). 

The  regions  of  the  body  are  less  uniform  in  breadth 
than  in  Campodea,  the  abdominal  segments  tapering 
away  from  the  much  broader  thorax  (see  PL  949).  The 
head  is  free  and  of  considerable  size. 

The  eyes  of  Lepisma  are  compound  but  they  have  only 
twelve  facets  (Packard),  so  that  they  are  primitive  in 
structure. 

A  pair  of  extremely  long  antennae  (see  PL  949)  are 
attached  to  the  head  and  a  pair  of  maxillary  palps  extend 
forward.  The  mouth  parts  in  Lepisma  are  hinged  to 


394  SYNOPTIC    COLLECTION. 

the  skull  by  an  imperfect  articulation  and  not  buried 
within  the  cavity  of  the  skull  as  in  Campodea.  They 
consist  of  a  pair  of  mandibles  (PL  951,  fig.  i)  and  two 
pairs  of  maxillae  (figs.  2,  3)  ;  the  two  parts  of  the  second 
pair  are  united  to  form  the  labium  (fig.  3).  At  the  tip  of 
the  labial  palpi  are  three  sense  organs. 

The  legs  are  similar  in  structure  and  are  flattened,  espe- 
cially the  large  basal  sections,  which  enables  this  little  ani- 
mal to  glide  in  and  out  of  crevices.  Each  leg  ends  in  a 
pair  of  claws.  The  forward  abdominal  appendages  of 
Campodea  are  replaced  in  Lepisma  by  clusters  of  stiff 
hairs,  but  the  seventh,  eighth,  and  ninth  segments  have 
abdominal  appendages  (PI.  951,  fig.  4),  and  the  extremity 
of  the  abdomen  is  provided  with  three  long  hairy  bristles 
and  a  pair  of  short  curved  bristles ;  hence  the  name  of 
Thysanura  or  bristle-tails.  In  the  female  there  is  an  ovi- 
positor (fig.  4)  composed  of  four  parts. 

The  tracheal  system  of  Lepisma  consists  of  ten  pairs 
of  spiracles,  and  the  tracheae  are  united  into  one  system 
consisting  of  two  longitudinal  trunks  and  of  cross  tubes.1 
The  tracheae  are  strengthened  by  delicate  spiral  threads 
(Fernald). 

It  has  been  shown  that  Lepisma  is  more  specialized 
than  Campodea  in  having  a  scale-protected  body,  exter- 
nal mouth  parts,  a  well  developed  ovipositor,  and  a  com- 
plete tracheal  system. 

Campodea  and  Lepisma  are  representative  Thysanuran 
insects,  having  the  abdominal  bristles  which  give  them 
the  name  of  bristle-tails.  In  this  same  order  is  the  sub- 
order Collembola  represented  by  the  Poduridae  or  spring- 
tails,  some  of  which  have  at  the  posterior  end  of  the 
abdomen  a  peculiar  spring  for  leaping.  This  is  seen  bent 
under'the  body  in  PI.  952,  which  is  a  side  view  of  Pap- 
irius  fuscus  Lubbock.  In  this  genus  the  leaping  organ 
extends  far  forward  and  the  tips  are  white.  Besides  the 

1  Sharp,  Cambridge  Nat.  Hist.,  V,  1895,  P-  l86- 


METAZOA INSECTA.  395 

spring,  many  of  the  Poduridae  have  a  sucker  attached  to 
the  basal  portion  of  the  abdomen  (see  PI.  952),  by  means 
of  which  the  insect  attaches  itself.  According  to  Uljanin 
quoted  by  Cholodkowsky  l  the  springing-fork  of  the  Pod- 
uridae arises  from  two  abdominal  appendages  which  are 
in  every  respect  similar  to  legs,  so  that  their  homology 
with  the  thoracic  limbs  is  hardly  open  to  doubt.  The 
ventral  tube  also  develops  from  two  anterior  abdominal 
appendages  tthich  are  probably  homologous  with  the 
thoracic  legs.  The  tiny  leapers  that  sometimes  blacken 
large  patches  of  our  snow,  making  it  appear  as  if  cov- 
ered with  animated  coal  dust,  are  spring-tails  (PL  953, 
Achorutes  nivicola  Fitch,  possibly  unnaturally  swollen). 
It  is  surprising  to  watch  the  leaps  of  these  minute  ani- 
mals, sometimes  covering  several  feet  (Comstock)  and 
again  jumping  many  times  their  height  into  the  air. 
Although  bluish  black  when  full  grown,  they  are  white 
when  young.2 

There  are  oth'er  Poduridae  which  have  a  spring  in  the 
larval  stage  but  which  lose  it  on  reaching  maturity.  One 
of  the  springless  forms  is  Lipura  maritima  Guer.  (PI. 
954).  This  is  one  of  the  few  insects  that  adapt  them- 
selves, for  short  periods  at  least,  to  salt  water.  It  is  found 
on  the  surface  of  tide  pools  and  immersed  in  the  water, 
but  when  in  this  situation  it  is  said  to  be  protected  by  a 
layer  of  air  that  envelops  its  body.8 

We  cannot  but  think  that  some  of  the  primitive  wing- 
less ancestors  of  insects,  which  in  all  probability  were 
essentially  like  the  Thysanura,  developed  in  the  course 
of  many  generations  the  wing  sacs  or  pads  that  finally 
became  efficient  organs  of  flight.  It  is  true,  as  before 
stated,  that  so  far  winged  insects  of  as  primitive  a  nature 
as  the  Thysanura  have  not  been  found  in  a  fossil  state, 
but  it  may  be  that  still  older  rocks  than  the  Devonian 

'Ann.  and  Mag.  Nat.  Hist.,  (6),  X,  1892,  p.  434. 

2  Packard,  5th  Ann.  Rep.  Peabody  Acad.  Sci.,  1872,  p.  30. 

3  Cambridge  Nat.  Hist.,  V,  1895,  P-  J95- 


396  SYNOPTIC    COLLECTION. 

will  reveal  insect  forms  that  are  marked  by  Thysanuran 
simplicity  of  structure,  and  by  the  possession  of  one  or 
two  pairs  of  wing  sacs.  Until  there  is  more  light  on  the 
subject  we  may  suppose,  as  Packard  1  points  out,  that  the 
dorsal  parts  or  nota  of  the  two  hinder  segments  of  the 
thorax  grew  out  laterally  in  some  running  or  leaping 
insect,  and  that  these  expansions  became  of  use  in  aiding 
to  support  the  body  in  its  longer  leaps.  Then  by  contin- 
ual use  they  would  become  articulated  to  the  body  and, 
growing  larger,  would  in  time  develop  into  permanent 
flying  organs  or  wings. 


Order  2. —  EPHEMEROPTERA.     (EPHEMERIDA,  Comstock.) 

One  of  the  earliest  winged  insects  found  in  America, 
known  as  Xenoneura  antiquorum  Scudd.,  was  a  synthetic 
form  which  possessed  affinities  with  several  generalized 
families,  among  them  the  Ephemerid'ae  or  mayflies. 
Although  the  wings  are  the  only  parts  of  these  ancient 
insects  preserved,  yet  nevertheless  they  have  become 
trustworthy  aids  in  determining  the  relationships  of  the 
insects  once  possessing  them. 

The  wing  of  Xenoneura  (PI.  955,  a  composite  drawing 
from  different  specimens)  exhibits  primitive  characters 
and  simple  venation,  indicating  slight  differentiation  of 
structure. 

Another  Devonian  insect,  Platephemera  antiqua  Scudd., 
was,  with  little  doubt,  an  ancestor  of  the  present  Ephe- 
meridae.  The  wings  (PI.  956,  the  dotted  lines  indicating 
the  probable  form  of  the  wing)  possess  unmistakable 
resemblances  to  the  same  organs  of  our  present  mayflies. 
The  drawing  is  made  to  show  the  expanse  of  the  wings, 
which  was  probably  about  135  mm.,  proving  that  this 
ancient  mayfly  was  much  larger  than  recent  species. 

1  3d  Rep.  U.  S.  Ent.  Comm.,  i88o-'82  (publ.  1883),  pp.  268-271. 


METAZOA INSECTA.  397 

In  the  Carboniferous  rocks  of  Commentry  an  insect, 
Homaloneura  bonneri  Brong.,  (PL  957,  a  restoration)  has 
been  discovered  which  Brongniart  considers  an  ancestor 
of  our  Ephemeridae.  It  has  a  large,  elongated,  and  plainly 
segmented  body,  a  sessile  abdomen  terminated  by  long 
caudal  setae  and  two  pairs  of  wings  of  equal  size.  Be- 
sides these  appendages  of  the  mesothorax  and  meta- 
thorax,  the  prothorax  has  a  pair  of  scale -like  appendages 
which  according  to  Brongniart  may  represent  prothoracic 
wings.  This  investigator  suggests  that  sometime  there 
may  be  found  in  the  ancient  strata  an  insect  with  six 
wings  or  rather  six  expansions  which  served  only  as  par- 
achutes, and  that  later  the  expansions  of  the  mesothorax 
and  metathorax  developed  into  useful  organs  of  flight  while 
those  of  the  prothorax  were  atrophied. 

The  living  Ephemeridae  in  a  very  early  larval  stage 
have  an  open  tracheal  system  like  that  of  Campodea,  with 
thoracic  spiracles.1  This  is  one  proof  of  their  descent 
from  ancestral  forms  possessing  an  open  tracheal  system. 
In  changing  their  habitat  from  land  to  water  they  have 
adapted  themselves  to  their  new  surroundings,  and  in  so 
doing  have  gradually  converted  the  open  tracheal  system 
into  a  closed  one.  At  the  same  time  external  gills  of 
varying  form  and  structure  have  developed.  In  fact,  so 
many  complex  modifications  have  arisen  in  these  insects, 
in  response  to  the  changed  environment,  that  it  is  difficult 
to  place  them  among  the  most  generalized  orders  unless 
we  bear  constantly  in  mind  the  general  features  of  the 
group.  These  are,  in  the  larvae,  a  long  body  (PL  958, 
fig.  i,  Chloeon  dimidiatum  Lubbock)  divided  into  freely 
movable  regions  ;  a  large  thorax  with  slight  consolidation 
of  the  prothorax,  mesothorax,  and  metathorax  ;  simple 
antennae ;  and  three  pairs  of  similar  legs. 

An  extremely  slow  development  is  often  attended  with 
numerous  sheddings  of  the  skin,  so  that  no  sharp  line  of 
demarcation  can  be  drawn  between  larva  and  pupa. 

1  Packard,  after  Dewitz,  Text-book  of  Ent.,  1898,  p.  460. 


398  v  SYNOPTIC    COLLECTION. 

In  Chloeon  as  many  as  twenty  moults  may  take  place. 
Up  to  the  ninth  moult  there  is  no  indication  of  wings, 
according  to  Lubbock.  At  the  twelfth  stage  the  posterior 
angles  of  the  mesothorax  and  metathorax  have  grown  out 
(fig-  3)-  The  mesothoracic  angles  grow  faster  than  the 
metathoracic  and  cover  the  latter  completely  (fig.  4). 
These  figures  are  interesting  as  showing  the  origin  of  the 
wing  pads  of  the  pupa.  When  the  last  skin  but  one  is 
thrown  off,  the  winged  insect  (fig.  5)  flies  away,  but  still 
another  skin  must  be  shed  before  full  size  is  attained  (fig. 
6,  C.  dipterum  Lubb.).  The  last  skin  is  often  got  rid  of 
while  on  the  wing.  We  shall  see  that  in  most  insects  this 
slow  process  of  development  is  more  or  less  shortened  by 
the  law  of  acceleration.  While  there  is  no  resting  period, 
there  is  a  metamorphosis  which  transforms  the  wingless 
insect  into  the  winged  creature.  It  is  evident  that  this 
metamorphosis  is  more  specialized  than  the  primitive 
development  of  the  Thysanura. 

The  generalized  characters  of  the  adult  (PL  958,  fig.  6  ; 
see  also  No.  959,  Hexagenia  bilineata  Say)  are  a  long, 
unconsolidated  body;  an  abdomen  without  an  ovipositor 
and  with  the  genital  openings  paired  ;  a  thorax  without 
secondary  sutures  and  with  wings  that  are  simple  in  their 
venation. 

The  adaptive  and  secondary  characters,  on  the  other 
hand,  are  seen  as  soon  as  the  young  larva  develops  tra- 
cheal  gills  (PL  958,  fig.  2  ;  see  also  figs.  3,  4)  on  each 
side  of  the  abdomen.  These  fit  it  for  an  aquatic  existence 
and  the  larval  and  pupal  life  may  last  three  or  four  years. 
The  long  caudal  setae  also  aid  as  respiratory  organs,  and 
the  terminal  blood  vessel  in  the  body  is  so  made  as  to 
drive  the  blood  backward  into  the  canals  of  the  setae,1 
where  it  is  purified  by  the  air  in  the  water. 


1  Zimmermann,  Zeitschr.  f.  wiss.  Zool.,  XXXIV,  1880,  p.  404. 
See  also  Creutzburg,  Ann.  and  Mag.  Nat.  Hist.,  (5),  XV,  1885,  p. 
494. 


METAZOA  —  INSECTA.  399 

An  advanced  pupal  stage  of  Chloeon  dipterum  Linn.,1 
is  seen  in  PI.  960.  The  wing  pad  on  the  left  side  and 
the  gills  on  the  right  side  have  been  cut  away.  In  addi- 
tion to  these  gills  the  pupa  has  caudal  gills  which  also 
serve  as  good  swimming  organs. 

The  adult  (PI.  958,  fig.  6,  C.  dipterum  Lubbock;  No. 
959)  is  specialized  by  reduction,  so  that  the  mouth  parts 
are  wholly  incapable  of  taking  food.  The  insect  in  this 
stage  lives  only  a  few  hours  or  at  most  a  few  days ;  hence 
the  name  Ephemeroptera  (signifying  short-lived  insect  and 
wing)  given  to  this  order.  When  the  function  of  repro- 
.duction  is  performed  the  insect  dies.  The  loss  of  efficient 
mouth  parts  is  correlated  with  a  loss  of  the  second  pair  of 
wings  (PI.  958,  figs.  5,  6;  No.  959)  and  with  a  peculiar 
modification  of  the  compound  eyes.  These  organs  are 
divided  in  Chloeon  so  that  there  appear  to  be  a  pair  of 
stalked  eyes  (which,  however,  are  not  united  at  their 
bases)  and  a  pair  of  sessile  eyes  (fig.  7).  Besides  these 
eyes  there  are  three  ocelli  (fig.  7). 

Peculiar  modifications  of  structure  are  found  among  the 
more  specialized  Ephemeridae.  An  extreme  case  of 
specialization  in  the  pupal  stage  is  seen  in  Prosopistoma 
foliaceum  Fourcroy  (PI.  961,  fig.  i,  x  12).  Here  a 
portion  of  the  mesothorax  and  metathorax  with  the  ante- 
rior wing  pads  has  formed  a  carapace  that  covers  the  dor- 
sal part  of  the  body  with  the  exception  of  the  four 
posterior  abdominal  segments  and  the  caudal  swimming 
organs.  This  carapace  conceals  from  view  the  respira- 
tory chamber  with  its  five  pairs  of  gi  Is  supplied  with 
tracheae.  The  water  passes  into  the  respiratory  chamber 
at  two  openings,  seen  on  either  side  in  the  ventral  view 
(fig.  2,0)  and  flows  out  at  the  dorsal  opening  (fig.  i,  0). 
In  the  ventral  view  (fig.  2)  the  last  segment  with  its 

1  Cloeon  dipterum  Linn.,  a  synonym  for  Chloeon  dipterum  Lubbock; 
see  Eaton,  Trans.  Linn.  Soc.  London,  (2),  Zool.,  Ill,  1888,  pp. 
183,  188. 


400  SYNOPTIC    COLLECTION. 

hairy  appendages   is    drawn  completely    into    the    ninth 
segment  of  the  abdomen. 

Specialization  by  reduction  is  illustrated  in  the  adult 
stage  by  Caenis  (PI.  962,  C.  macrura)  in  which  the  second 
pair  of  wings  have  disappeared  and  the  insect  resembles 
the  two-winged  Diptera. 


Order  3.  —  ODONATA. 

These  insects,  like  the  Ephemeroptera,  have  become 
adapted  to  aquatic  life.  There  can  be  little  doubt,  how- 
ever, that  their  ancestors  were  terrestrial,  air-breathing 
animals  with  an  open  tracheal  system  like  that  of  Campo- 
dea. 

A  dragon-fly,  Palaeophlebia  superstes  (PI.  963,  fig.  i, 
with  the  wings  on  one  side  and  with  two  legs  removed) 
has  been  discovered  in  Japan,  which  possesses,  perhaps, 
more  primitive  characters  than  any  other  member  of  its 
order.  Unfortunately  the  larval  form  is  unknown,  but 
judging  from  the  adult,  the  larva  must  be  more  primitive 
than  most  young  dragon-flies.  The  broad  head,  the 
separated  eyes  (fig.  2),  the  nearly  equal  wings,  with  their 
simple  venation  (fig.  i),  are  all  generalized  characters. 
Although  it  is  true  that  the  larvae  of  the  Odonata  do  not 
resemble  Campodea  so  closely  as  the  larvae  of  the. 
Ephemeridae,  nevertheless,  the  body  in  the  most  general- 
ized family,  represented  by  Calopteryx  (spelled  also 
Calepteryx)  virgo  (PI.  964,  fig.  i  ;  No.  965,  an  allied 
form,  Hetaerina)  is  long  with  little  concentration  of  regions 
and  but  slight  modification  of  the  thoracic  segments. 
Like  the  young  mayfly,  the  young  Calopteryx  has  three 
caudal  appendages  (fig.  i)  which  serve  both  as  locomo- 
tor  and  as  respiratory  organs. 

The  second  pair  of  maxillae  or  labium  have  become 
modified  into  a  mask  (fig.  2),  so  called  because  in  the 
more  specialized  genera  it  entirely  conceals  the  mandibles 


METAZOA INSECTA.  401 

and  first  pair  of  maxillae.  It  can  be  thrown  out  as  rep- 
resented in  the  figure,  and  the  teeth  at  the  end  serve  to 
catch  the  prey. 

According  to  Packard,1  it  was  owing  to  the  fact  that 
the  second  pair  of  maxillae  were  armed  with  teeth  that 
the  name  Odonata  (from  the  Greek  meaning  tooth)  was 
given  to  this  order.  Calvert2  remarks,  however,  that  the 
name  refers  "  presumably  to  the  toothed  mandibles/' 

The  adult  has  small  eyes,  comparatively  speaking ;  the 
labium  is  reduced  in  size  and  the  parts  are  more  concen- 
trated than  in  the  larva,  although  much  more  loosely  con- 
nected than  in  the  specialized  dragon-flies. 

In  many  ways  Agrion  (No.  966)  resembles  Cajppteryx. 
Its  young  is  provided  with  three  caudal  gills.  The  head 
of  the  adult  is  broad  with  the  eyes  on  the  sides,  and  the 
labium  is  short.  The  wing  venation  is  simple  and  the 
flight  is  not  swift.  The  long  slender  abdomen  is  used  as 
a  rudder  and  is  sometimes  brilliantly  colored  in  both 
genera. 

The  most  specialized  Odonata  are  represented  by 
Aeschna  and  Plathemis  (=  Libellula).  Aeschna  (PI.  967  ; 
No.  968)  is  one  of  our  largest  dragon-flies.  The  eyes 
are  separated  in  the  larval  and  pupal  (PI.  967,  A.  grandis 
Linn.)  stages  but  meet  on  top  of  the  head  in  the  adult 
(No.  968,  A.  heros  Fabr.).  The  wing  muscles  are  strong 
and  the  flight  is  swift,  the  insect  darting  like  an  arrow. 

Plathemis  is  another  swift  flier.  Its  eggs,  like  those  of 
most  Odonata  (see  No.  969),  are  laid  on  aquatic  plants  or 
dropped  in  the  water.  The  young  (No.  970  ;  PI.  97  j,  fig. 
i)  possesses  the  long  unconsolidated  body  and  the  simi- 
lar thoracic  segments  of  the  adult  Thysanura  and  the 
larval  Ephemeridae,  but  in  many  respects  it  has  become 
specialized.  The  labium  is  modified  into  a  mask  (No. 
972)  that  completely  covers  the  other  mouth  parts.  The 


1  Ent.  for  Beginners,  1889,  p.  346. 

2  Trans.  Amer.  Ent.  Soc..  Phila.,  XX,  1893,  P-  J53- 


402  SYNOPTIC   COLLECTION. 

young  Plathemis,  it  may  be  a  larva  or  a  pupa  (PI.  971,  fig. 
2),  looks  extremely  innocent  until  a  little  crustacean  or 
insect  passes  by,  then  suddenly  the  mask  is  darted  out, 
as  seen  in  No.  972,  also  PI.  971.  fig.  2,  and  the  prey  is 
secured.  The  legs  of  both  larva  and  pupa  are  extremely 
long.  The  rudiments  of  wings  appear  after  the  third  or 
fourth  moult l  and  with  their  development  the  segments 
of  the  thorax  become  greatly  modified. 

The  larval  and  pupal  Plathemis  breathes  by  tracheal 
gills  situated  in  the  rectum  at  the  posterior  end  of  the 
body.  These  gills  are  in  the  form  of  lamellae  (fig.  3, 
Plathemis  vulgate}  which  are  richly  supplied  with  tracheae 
(fig.  3).,  Instead  of  having  three  caudal  gills  at  the  end 
of  the  abdomen,  like  the  young  Calopteryx  and  Agrion, 
Plathemis  has  three  chitinous  valves  (PI.  971,  figs.  2,5; 
No.  972).  When  these  open,  water  fills  the  rectum  and 
the  tracheal  gills  rob  it  of  its  air ;  then  it  is  thrown  out 
with  such  force  as  to  send  the  insect  swiftly  forward.  In 
this  way  the  water  serves  the  double  purpose  of  locomo- 
tion and  respiration. 

The  pupal  life  lasts  eight  or  ten  months  and  during  this 
time  several  moults  take  place.  PI.  971,  fig.  4,  is  a  side 
view  of  the  last  pupal  skin  shed  by  a  male  Plathemis  tri- 
maculata  De  Geer,  and  fig.  5  is  a  dorsal  view  of  the  pupal 
skin  (No.  973)  shed  by  a  female  of  the  same  species. 
The  former  was  drawn  from  a  dry  specimen,  the  latter 
from  No.  973,  which  had  then  been  in  alcohol  a  short 
time.  Both  figures  show  the  four  tracheal  threads  that 
extended  from  the  inner  side  of  the  pupa  skin  to  the 
emerging  dragon-fly,  and  which  were  shed  with  the  skin 
when  the  dragon-fly  escaped. 

The  adult  Plathemis  trimaculata  De  Geer  (No.  974,  $  ; 
No.  975,  9  ;  PI.  976,  dissection  of  9  ) ,  retains  the  primi- 
tive character  of  the  ten  distinct  abdominal  segments,  but 
various  remarkable  modifications  have  taken  place  in  the 

1  Quoted  from  Poletaiew  by  Calvert,  loc.  «?.,  p.  197. 


METAZOA  —  INSECTA.  403 

head  and  thorax  whereby  the  insect  is  fitted  for  its  aerial 
life.  The  unusual  habit  of  catching  its  food  while  on  the 
wing  has  caused  the  head  to  become  extremely  mobile. 
It  seems,  indeed,  as  if  the  dragon-fly  could  turn  this  part 
of  its  body  completely  round  without  the  slightest  injuri- 
ous effect.  The  head  is  aided  by  the  long  slender  legs 
(PI.  976,  fig.  i)  which  have  lost  their  function  of  walking 
and  changed  their  position,  being  much  farther  forward 
on  the  thorax  than  in  other  insects,  as  seen  in  the  side 
view  (fig.  2).  Calvert l  states  that  the  first  pair  of  legs 
are  usually  employed  in  holding  the  food  while  it  is 
devoured. 

These  peculiar  habits  have  doubtless  brought  about  the 
complex  structure  of  the  thorax.  The  prothorax  (fig. 
i,/)  which  in  the  larva  (PI.  971,  fig.  i)  was  about  the 
size  of  the  other  two  segments  of  the  thorax,  has  become  a 
tiny  ring,  while  the  mesothorax  (PI.  976,  figs.  1,2,  ms)  and 
the  metathorax  (figs,  i,  2,  mt)  are  large  and  consolidated. 
These  contain  the  powerful  muscles  that  control  the 
action  of  the  wings.  The  two  pairs  of  wings  (fig.  i)  are 
similar  in  size  and  structure,  and  each  pair  is  free  from 
the  other,  which  is  unusual  in  fast  fliers.  To  understand 
fully  what  a  complicated  machine  it  is  that  produces  the 
flight  of  dragon-flies,  one  needs  to  examine  von  Lenden- 
feld's  figures 2  of  the  thorax  and  wings  of  these  insects. 
It  is  indeed  surprising  that  such  complexity  is  found  to 
exist  among  the  more  generalized  orders  of  this  class  of 
animals. 

Authorities  differ  in  regard  to  the  tracheal  system  of 
the  Odonata,  but  according  to  Calvert  3  there  are  two 
pairs  of  spiracles  in  the  thorax  and  a  pair  in  each  of  the 
abdominal  segments  from  the  second  to  the  eighth  inclu- 


1  Loc.  cit.,  p.  162. 

2Sitzungsb.  k.  Akad.   d.    Wiss.    Wien,  LXXXIII,  Th.  i,  1881, 
pp.  289-380,  pis.  1-7. 

3  Trans.  Amer.  Ent.  Soc.,  Phila.,  XX,  1893,  pp.  161,  170. 


404  SYNOPTIC   COLLECTION. 

sive.  It  is  interesting  to  note  that  even  in  these  more 
generalized  insects  the  social  instinct  is  developed  in  so 
far  that  the  migrating  habit  has  been  acquired,  Plathemis 
quadrimaculata  Linn.,  having  been  seen  frequently  mi- 
grating in  large  numbers. 

Order  4.  —  PLECOPTERA. 

The  larvae  of  the  stone-flies  or  Perlids  resemble  in  a 
general  way  the  Thysanura  and  also  in  their  adaptive 
features  the  larvae  of  the  Ephemeridae.  Like  the  latter 
they  are  fitted  for  an  aquatic  life,  as  seen  in  PL  977, 
which  is  the  larva  of  a  species  of  Perla  showing  Thysan- 
uran  characters  and  in  addition  the  adaptive  tracheal 
gills. 

The  motions  of  the  larva  and  pupa  are  slow.  The 
pupa  (PL  978,  fig.  i,  Perla  virescens),  however,  has  no 
resting  period  and,  although  the  skin  is  shed  several 
times,  the  form  of  the  larva  is  preserved  essentially  in  the 
adult  (fig.  2,  with  the  wings  extended;  see  also  No.  979). 
When  the  wings  are  folded  (fig.  3)  they  are  plaited  and 
hence  the  name  Plecoptera,  from  the  Greek  signifying 
plaited  wing. 

It  is  unusual  for  the  tracheal  gills  of  the  larva  to  be 
retained  by  the  adult,  but  this  is  the  case  in  Pteronarcys 
(PL  980,  ventral  side),  where  there  are  eight  sets  of 
branchial  tufts.  According  to  Hagen,1  these  vestiges  are 
in  a  shriveled  condition  and  are  functionally  useless. 

Among  the  Perlids,  the  genus  Nemoura  or  the  willow-fly 
contains  a  species  (N.  postica  Walk.)  with  well  developed 
wings,  while  the  male  of  another  species  (N.  trifasciata} 
has  the  forward  pair  existing  only  as  vestiges.  In  this 
genus  the  mandibles  are  horny  and  provided  with  teeth, 
while  in  most  of  the  Perlidae  they  are  membranous. 

1  Quoted  by  Sharp,  Cambridge  Nat.  Hist.,  V,  1895,  p.  402. 


METAZOA INSECTA.  405 

As  a  ru'e  among  insects,  whenever  there  is  a  decrease 
in  the  size  of  the  wings,  it  occurs  in  the  female,  while  the 
wings  of  the  male  are  often  remarkably  large,  but  there 
is  a  species  among  the  Plecoptera,  the  Isogenus  nubecula 
(PI.  981,  figs,  i,  2),  in  which  the  wings  of  the  female 
(fig.  i)  are  large,  while  those  of  the  male  (fig.  2)  are 
reduced  to  remnants. 


Order  5.  —  PLATYPTERA. 

The  termites  possess  certain  Thysanuran  characters  in 
the  larval  state,  while  in  maturity  they  are  developed 
physiologically  to  a  greater  degree  than  any  other  mem- 
bers of  the  generalized  orders  of  insects. 

The  larva  of  Termes  (No.  982  ;  PI.  983,  fig.  i,  T.  luci- 
fitgus)  has  distinct  thoracic  and  abdominal  segments  and 
the  two  regions  are  broadly  connected.  It  is  white  and 
even  the  hooks  of  the  feet  are  colorless,  while  the  mandi- 
bles are  tinted  only  slightly.  This  condition  indicates 
that  the  larvae  do  little  work,  and  this  is  the  case,  since 
they  are  nursed  and  carefully  tended  when  young  and  are 
not  obliged  to  shift  for  themselves. 

The  pupae  (No.  984;  PI.  983,  fig.  2)  are  essentially 
like  the  larvae  excepting  in  possessing  wing  pads. 

When,  however,  the  adult  forms  are  considered,  we 
find  conditions  wholly  different  from  anything  so  far 
described.  The  law  of  variation  has  acted,  and  speciali- 
zation in  function  has  produced  modifications  in  structure. 
At  the  same  time  the  social  instinct  has  developed  to  a 
remarkable  degree  so  that  there  appears,  as  a  result,  a 
colony  consisting  of  groups  of  many  individuals,  each 
group  having  its  special  work  to  perform. 

If  the  course  of  development  had  been  typical,  that  is 
to  say,  if  it  had  been  similar  to  that  of  most  insects,  the 
pupae  would  develop  in  every  case  into  the  male  or 
the  female  winged  insect  (No.  985,  J  ;  No.  986,  winged 


406  SYNOPTIC    COLLECTION. 

form;  also  see  PI.  983,  fig.  3)  with  two  pairs  of  wings. 
It  so  happens,  however,  that  this  occurs  with  only  com- 
paratively few  members  of  the  colony.  The  winged 
insects  swarm  ;  that  is,  they  leave  the  nest  together,  and 
after  this  "marriage  flight"  new  colonies  are  probably 
founded,  although  Grassi 1  concludes  after  prolonged 
investigations  that  no  further  result  attends  swarming 
than  a  wholesale  slaughter  of  the  individuals.  This  view 
is  strengthened  by  Hagen2  who  witnessed  a  swarm  of 
termites  attended  by  fifteen  species  of  birds,  and  some 
of  these  were  so  gorged  with  termites  that  they  could 
not  close  their  beaks. 

While  it  may  be  true,  as  heretofore  generally  stated, 
that  the  colonies  of  some  species  are  founded  by  the 
wingless  and  helpless  king  and  queen  that  re-enter  the 
nest  after  "  the  flight"  just  mentioned,  it  seems  now  more 
probable  that  these  two  are  not  in  such  a  weakened  con- 
dition as  described,  but  that  they  gradually  become  so 
after  remaining  in  the  nest  and  being  waited  upon  by  the 
workers.  Generally  speaking,  Grassi  considers  that  when 
the  vitality  of  the  queen  is  exhausted  (which  probably  is 
not  the  case  for  several  years)  one  of  the  complemental 
females  (PI.  983,  fig.  5),  which  are  always  kept  for  the 
purpose,  is  substituted  in  her  place,  and  thus  the  continu- 
ation of  the  species  is  secured. 

The  king  when  found  in  the  royal  chamber  of  the  nest 
is  wingless  (No.  987,  J!  bellicosus  Smeath).  PL  988, 
fig.  i,  represents  the  wingless  king  of  a  species  of  Termes 
from  Singapore.  The  queen  found  with  the  king  is  seen 
in  fig.  2,  both  natural  size. 

The  body  of  the  queen  becomes  enormously  distended 
with  eggs  (PL  983,  fig.  4,  T.  lucifugus ;  No.  989,  queen 
of  T.  bellicosus  Smeath. ;  No.  990,  royal  chamber  of  the 
same).  According  to  Sharp  growth  actually  takes  place 

1  Atti  Accad.  Gioenia,  Catania,  VI,  1893. 

2  Proc.  Boston  Soc.  Nat.  Hist.,  XX,  1881,  p.  118. 


METAZOA INSECTA. 


407 


after  the  metamorphosis  which  is  the  only  instance  known 
among  insects.  This  growth  does  not  affect  the  chitinous 
segments  which  are  close  together  before  egg-bearing 
begins,  and  afterward  far  apart  (PI.  983,  fig.  4;  see  also 
PL  988,  fig.  2). 

Besides  the  young  and  the  winged  and,  later  in  life,  the 
wingless  males  and  females,  there  are  workers  and 
soldiers  in  the  colony  of  T.  lucifugus.  The  larvae  which 
produce  these  different  forms  are  all  alike,  and  it  is  prob- 
able that  the  duties  which  have  devolved  upon  certain 
members  of  the  colony,  generation  after  generation,  have 
been  one  cause  of  the  loss  of  wings.  The  more  immediate 
cause  lies  in  the  physical  condition  of  food  which  is  of 
such  a  nature  as  to  divert  the  larvae  from  the  usual 
course  of  development  and  to  equip  the  adults  for  a  spe- 
cial work. 

Although  the  worker  of  Termes  (PI.  983,  fig.  6  ;  No. 
991)  is  apparently  more  like  the  larva  than  the  winged 
insects,  yet  in  reality  it  is  farther  removed  from  the  larval 
form,  since  its  ancestors  were  doubtless  winged  creatures 
whose  descendants  gradually  lost  their  wings  by  ceasing 
to  fly,  and  by  becoming  laborers  for  the  colony  in  the  way 
of  building  and  repairing  nests,  storing  food,  feeding  the 
young,  etc.  In  doing  this  work  they  have  become  more 
hardy  and  are  provided  with  dark-colored  mandibles  and 
feet. 

Still  greater  specialization  along  the  same  line  results 
in  the  termite  soldier  (PI.  983,  fig.  7  ;  No.  992).  Its 
head  is  immense  for  so  small  a  body,  and  all  its  parts  are 
more  or  less  modified.  The  mandibles  are  powerful  and 
the  whole  organization  is  that  of  a  fighter. 

According  to  the  view  just  stated  the  worker  and 
soldier  are  termites  which  have  come  to  their  present  con- 
dition by  a  process  of  specialization,  and  are  not  illustra- 
tions of  arrested  development  as  maintained  by  some 
naturalists.  If  they  were  such  illustrations,  they  might 
be  placed  side  by  side  with  the  larvae.  But,  on  the  con- 


408  SYNOPTIC    COLLECTION. 

trary,  they  are  adults  which  are  differentiated  in  a  peculiar 
way  for  a  particular  sphere  of  action,  thereby  becoming 
examples  of  specialization  by  the  suppression  of  organs. 

An  interesting  modification  in  structure  for  the  pur- 
pose of  defence  is  found  in  the  soldier  of  the  genus  Eu- 
termes  (PL  993,  figs.  1-6).  Its  head  (fig.  5  ;  fig.  6,  x  25) 
extends  forward  into  a  beak  or  "gun  "  and  from  this  beak 
the  animal  discharges  glutinous  pellets  or  shot l  which 
are  so  sticky  that  its  enemy  is  quickly  disabled.  Eu- 
termes  is  one  of  the  smaller  termites ;  the  figures  of  the 
worker  (fig.  4)  and  of  the  soldier  are  enlarged  five  diam- 
eters, and  the  remaining  three  figures  are  natural  size. 
The  winged  female  is  seen  in  fig.  i,  and  the  wingless 
queen,  before  the  period  of  egg-bearing  begins,  in  fig.  2, 
while  fig.  3  is  the  mature  queen  with  her  body  distended 
with  eggs. 

The  wings  of  the  termites  when  extended  are  broad, 
and  hence  the  name  of  Platyptera  (meaning  broad  wing). 
When  spread  they  give  an  unusually  broad  effect  to  the 
insect.  They  are  about  equal  in  size  and  structure  in  the 
termites  and  hence  the  name  Isoptera  which  is  often 
given  to  this  order. 

Oligotoma  michaeli  McLachlan  (PL  994,  fig.  i,  larva; 
fig.  2,  "starved"  pupa;  fig.  3,  adult)  of  the  family  Em- 
biidae,  is  interesting  for  the  reason  that  it  represents  a 
case  among  insects  in  which  both  pairs  of  wings  are 
developed,  but  which  are  so  weak  that  they  are  practi- 
cally useless.  The  thoracic  segments  to  which  these  in- 
efficient organs  are  attached  are  unconsolidated  and  the 
insect  is  described  as  "feeble."  It  seems  as  though  the 
wings  were  ready  to  drop  off  and  in  time  Oligotoma 
would  become  wingless. 

The  Psocidae  are  like  the  termites  in  many  ways  but 
the  arrangement  of  the  veins  of  the- wings  differs  from 
that  of  any  biting  insect  (Comstock)  and  these  organs 

1  Dudley,  Trans.  N.  Y.  Acad.  Sci.,  VIII,  1889,  p.  87. 


METAZOA INSECTA.  409 

are  not  of  equal  size  (PI.  995,  Psocus  venosits  Burm.), 
although  when  extended  they  give  a  broad  effect  to  the 
insect.  When  not  flying  the  wings  are  held  roof-like  and 
almost  vertically  over  the  body. 

Very  little  is  known  of  the  life  history  of  the  Psocidae, 
but  it  is  interesting  to  note  that  they  spin  a  web  as  a 
covering  for  their  eggs.  They  are  further  represented 
by  Psocus  fasciatus  F.  (PI.  996,  fig.  i),  Mesopsocus  uni- 
punctatits  Mull.  (fig.  2,  9  ),  and  Atropos  divinatoria  Mull, 
(fig.  3).  Psocus  is  provided  with  four  delicate  wings; 
the  male  Mesopsocus  has  the  same  number,  while  the 
female  (fig.  2)  has  only  vestiges  of  these  organs  (white 
in  the  drawing),  and  Atropos  is  altogether  destitute  of 
them.  Large  numbers  of  the  latter  genus  are  sometimes 
found  gnawing  books  and  papers  and  for  this  reason 
they  are  known  as  "book-lice,"  although  they  are  not 
parasites  and  have  not  the  structure  of  true  lice. 

In  England  the  Atropos  is  called  the  "death  watch," 
on  account  of  a  ticking  sound  the  insect  is  supposed  to 
make.  The  Psocidae  bear  a  striking  resemblance  to  the 
Aphides  of  the  order  Hemiptera,  but  unlike  the  Aphides 
the  Psocidae  have  biting  mouth  parts. 

The  family  Mallophagidae  we  place  provisionally  as 
the  most  specialized  of  the  Platyptera.  The  ancestors 
and  primitive  forms  of  the  family  are  as  yet  unknown, 
and  the  life  history  of  the  group  has  not  been  worked 
out  completely,  but  enough  has  been  discovered  to  show 
that  these  insects  differ  essentially  from  the  well  estab- 
lished orders.  This  has  caused  many  entomologists  to 
place  them  as  an  independent  order,  the  Mallophaga. 
This  word  is  from  the  Greek,  meaning  to  eat  wool,  and 
refers  to  the  habit  which  some  of  the  species  have  of  eat- 
ing the  wool  or  hair  of  sheep  and  goats.  Most  of  the 
species,  however,  live  upon  the  feathers  of  birds.  All 
the  forms  are  parasitic  throughout  life  and  are  examples 
of  specialization  by  reduction.  PI.  997,  figs.  1-4.  illus- 
trates one  of  the  "bird-lice,"  Lipeurus  forficulatus  N., 


410  SYNOPTIC    COLLECTION. 

found  on  the  pelican,  and  which  is  related  to  Nirmus 
daviformis  Denny  (PI.  998,  fig.  i),  and  to  the  common 
hen-louse,  Menopon  pallidum  Nitzsch  (the  colqr  of  the 
last  species  is  shown  in  figure  2  of  PI.  998,  while  the 
details  of  structure  are  better  seen  in  PI.  999).  Accord- 
ing to  Kellogg,1  to  whom  we  are  indebted  for  most  of  the 
facts  in  this  description,  the  eggs  of  Lipeurus  are  fastened 
singly  to  the  vanes  of  the  feathers  of  the  host,  and  the 
young  (PI.  997,  fig.  i)  is  a  parasite  at  start.  Its  head  is 
large  in  proportion  to  the  size  of  the  body,  and  the  tho- 
rax, even  at  this  early  stage,  is  apparently  made  of  only 
two  segments,  the  mesothorax  and  metathorax  being 
united  without  visible  suture.  This  union  is  doubtless 
a  vestige  of  the  time  when  the  insect  possessed  two  pairs 
of  wings  and  was  a  flier ;  it  is  also  a  proof  that  Lipeurus 
is  a  secondary  and  not  a  primitive  animal. 

In  the  main,  the  young  (fig.  2,  an  older  stage)  and  the 
adult  (fig.  3,  9  ;  fig.  4,  $~)  resemble  each  other.  This 
resemblance,  however,  cannot  be  compared  with  the  re- 
semblance of  the  larval  and  adult  Thysanura,  since  in 
this  case  of  the  Mallophaga  we  have  not  primitive  sim- 
plicity but  on  the  contrary  a  specialized  larva  fitted  for 
a  parasitic  life.  The  body  is  extremely  flattened  and 
hardened  by  chitin.  The  biting  mouth  parts  are  modi- 
fied for  cutting  feathers  or  hair,  bits  of  which  are  seen 
in  the  crop  through  the  seinitransparent  walls  of  the  body. 
In  some  species  the  upper  lip  serves  as  a  scraper  and  the 
mandibles  are  provided  with  sharp  teeth.  The  feet  ter- 
minate in  claws  for  clinging,  while  the  fore  legs  are  used 
as  foot-jaws  for  carrying  food  to  the  mouth. 

The  wing  muscles  are  greatly  reduced  in  size  and  there 
are  no  indications  of  wings  in  any  stage  of  any  species 
of  the  group. 

While  it  is  true  that  these  insects  are  parasites,  they 

1  Leland  Stanford  Junior  Univ.,  Contrib.  Biol.  Hopkins  Seaside 
Lab.,  IV,  1896. 


METAZOA INSECTA.  411 

are  not  so  extremely  modified  as  many  among  the  more 
specialized  orders,  such  as,  for  instance,  Melophagus  ovi- 
nus  Linn.,  the  sheep-tick  of  the  Diptera.  The  Mallo- 
phaga  still  have  the  generalized  type  of  mouth  parts  and 
the  power  of  locomotion. 

Order  6.  —  EUPLEXOPTERA. 

The  larval  characters  of  this  order  are  mostly  primi- 
tive and  generalized,  but  little  is  known  of  the  develop- 
ment or  life  history  of  the  group. 

Unlike  most  insects  the  mother  earwig  does  not  die 
soon  after  laying  her  eggs,  but  according  to  Kirby  she 
broods  "over  her  eggs  and  young  almost  like  a  hen."  1 

PI.  looo,  fig.  i,  is  the  larva  of  the  common  earwig, 
Forficula  auriciilana  Linn.  The  thorax  and  abdomen 
are  distinctly  segmented,  and  the  junction  of  the  two  is 
broad.  The  caudal  appendages,  even  at  this  early  stage, 
are  in  the  form  of  forceps. 

The  adult  (PI.  1000,  fig.  2  ;  No.  1001)  retains  the  long 
body  of  the  larva,  the  distinct  thoracic  segments,  and  the 
biting  mouth  parts.  There  is  a  peculiar  imbricated  ar- 
rangement of  the  segments,  however,  which  we  have  not 
seen  in  the  insects  so  far  described. 

The  wings  of  the  adult  are  unique.  The  anterior  pair 
are  reduced  in  size  and  are  chitinous  covers  for  the  hind 
wings,  which  are  large  and  rounded  when  spread  (PI. 
1000,  fig.  3),  but  which  by  an  ingenious  method  can  be 
folded  and  almost  wholly  packed  away  under  the  wing 
covers  (fig.  4)  ;  hence  the  name  of  the  order  Euplexop- 
tera,  meaning  to  fold  well  and  wing.  The  projecting  por- 
tions of  the  wings,  unlike  the  remaining  parts,  have  the 
same  texture  and  sculpturing  as  the  wing  covers. 

No  one  knows  what  has  caused  the  earwig  to  fold  its 

1  Text-book  of  Ent.,  1885,  p.  81. 


412  SYNOPTIC    COLLECTION. 

wings  in  this  fashion,  and  the  subject  becomes  more 
interesting  when  we  consider  that  "  it  is  probable  that  the 
majority  of  the  individuals  of  this  species  may  never  make 
use  of  their  organs  of  flight  or  go  through  the  complex 
process  of  unfolding  and  folding  them."  1  If  this  is  the 
case  this  species  of  earwig  is  an  illustration  of  an  animal 
that  possesses  absolutely  useless  organs.  These  organs 
occur,  however,  in  an  order  of  insects  all  of  whose  mem- 
bers have  vestigial  fore  wings,  and  many  of  whose  members 
are  without  either  pair  of  wings.  One  may,  therefore, 
reasonably  predict  that  in  time  Forficula  auricularia  Linn., 
will  be  wingless. 

The  forceps  which  have  given  the  name  of  Forficulidae 
to  the  family  probably  represent  the  cerci  of  many  insects. 
They  vary  greatly  in  form  from  symmetrical  to  distorted 
organs  and  little  is  known  in  regard  to  their  function.  It 
is  now  probable  that  the  peculiar  insect,  Hemimerus  tal- 
poides  Walk.  (PI.  1002,  fig.  i,  young;  fig.  2,  adult),  is  a 
near  relative  of  Forficula.  According  to  the  observations 
of  Hansen,2  this  insect  has  not  four  pairs  of  mouth  parts, 
as  has  been  stated,  but  the  normal  number  of  three  pairs. 

Hemimerus  is  a  blind,  wingless  creature,  that  is  found 
living  among  the  hairs  of  the  rat,  Cricetomys  gambianus, 
Waterh.  Its  development  is  accelerated,  so  that  it  brings 
forth  living  young,  but  it  differs  from  other  viviparous 
insects  by  giving  birth  to  only  one  at  a  time.  Probably 
several  days  intervene  between  the  birth  of  the  small 
number  of  offspring.  Fig.  i  represents  the  young  as 
taken  from  the  mother,  showing  the  coiled  position 
and  the  ragged  end  of  a  process,  extending  from  the 
neck,  which  Hansen  thinks  connects  the  embryo  with 
the  mother.  When  uncoiled  the  young  Hemimerus  is 
nearly  as  large  as  the  parent,  and  differs  from  it  only 
in  the  number  of  antennal  joints  and  in  the  structure 
of  the  posterior  abdominal  segments. 


,  Cambridge  Nat.  Hist.,  V,  1895,  p.  207. 
2Ent.  Tidskr.,  XV,  1894. 


METAZOA INSECTA.  413 

The  Euplexoptera  are  placed  by  many  entomologists 
among  the  Orthoptera,  the  next  order  to  be  described, 
but  it  will  be  seen  that,  while  they  possess  certain  charac- 
ters in  common  with  that  order,  they  are  in  other  essen- 
tial respects  very  dissimilar. 

Until  at  least  there  is  more  knowledge  in  regard  to  the 
life  history  of  the  Euplexoptera  it  seems  better  to  place 
them  in  a  distinct  order  next  the  Orthoptera. 

Order  7. —  ORTHOPTERA. 

The  ancestors  of  the  Orthoptera  or  straight-winged 
insects  are  found  in  the  Carboniferous  and  possibly  in 
the  Silurian  formations.  PI.  1003  represents  one  of 
these  primitive  forms,  Progonoblattma  columbiana  Scud- 
der,  which  is  related  to  the  Blattidae  or  cockroaches  of 
to  day. 

The  body  in  these  ancient  cockroaches  was  elongated 
and  the  thoracic  segments  were  of  nearly  equal  size, 
while  the  junction  of  the  thorax  and  abdomen  was  broad. 

The  antennae  were  thread-like  and  the  mouth  parts 
were  of  the  biting  type.  The  legs  were  adapted  for  run- 
ning, and  the  two  pairs  of  wings  were  of  more  nearly 
equal  size  and  texture  than  the  wings  of  their  descend- 
ants. The  venation  of  these  organs  was  less  differen- 
tiated than  in  modern  types,  though  there  was  a  general 
resemblance,  the  principal  veins  and  their  branches 
running  to  the  outer  margin. 

Some  points  in  the  embryology  of  the  cockroaches  of 
to-day  are  instructive.  In  these  cockroaches  the  eggs 
and  embryos  are  protected  by  an  egg-case  in  which  are 
placed  sixteen  eggs  or  eight  on  each  side.  PI.  1004,  fig. 
i,  gives  an  external  view  of  this  case,  and  fig.  2  an  in- 
ternal view  showing  the  eight  eggs  on  one  side.  Ac- 
cording to  Cholodkovsky 1  the  segmentation  of  the 

.1  Zeitschr.  f.  wiss.  Zool.,  XLVIII,  1889. 


414  SYNOPTIC    COLLECTION. 

anterior  part  of  the  body  of  the  cockroach  may  be  seen 
at  first  distinctly.  In  the  course  of  the  development  a 
pair  of  appendages  appears  on  each  segment.  PI.  1005, 
fig.  i,  shows  one  pair  of  antennae,  three  pairs  of  mouth 
parts,  three  pairs  of  thoracic  legs,  and  eleven  pairs  of 
abdominal  appendages,  making  in  all  eighteen  pairs. 
These  are  alike  when  first  formed  and  appear  before  the 
dorsal  portion  of  the  body  is  completed.  Most  of  the 
abdominal  appendages  (which  we  have  already  found  in 
the  adult  Thysanuran  insects)  quickly  disappear,  as 
shown  in  the  older  embryonic  stages  (figs.  2,  3).  The 
body  shortens  but  the  distinctness  of  the  segments  is 
preserved.  The  eyes  (fig.  3,  c)  are  plainly  seen  in  this 
stage.  The  larvae  (No.  1006,  Blatta  (=  Periplanetd) 
orientalis  Linn.)  have  ancestral  and  Thysanuran  charac- 
ters, but  in  addition  the  adults  have  certain  marked 
adaptive  features.  Some  of  these  features  are  particu- 
larly well  shown  in  Blatta  orientalis  Linn.  (Nos.  1007, 
$  ;  1008  9)  and  in  the  large  Cuban  cockroach  (No. 
1009),  because  in  these  species  the  features  have  been 
intensified  by  domestication.  The  body  and  leg  sections 
are  extremely  flattened,  and  the  freely  movable  segments 
of  the  abdomen  can  be  extended  or  shortened  by  tele- 
scopic action,  thus  enabling  the  insect  to  crawl  into  nar- 
row crevices.  The  head  is  reduced  in  size  and  turned 
under  the  large  prothorax,  so  that  it  is  scarcely  seen  in  a 
view  from  above.  The  biting  mouth  parts  are  hard  and 
dark  colored,  since  the  cockroach  feeds  upon  almost  any 
substance  that  comes  in  its  way. 

Both  pairs  of  wings  are  well  developed  in  certain 
genera  of  this  family,  Blabera  for  instance  (PI.  1010,  fig. 
i,  A,  anterior  wing;  B,  posterior  wing),  but  in  Blatta  the 
wings  of  the  male  (No.  1007)  are  diminished  in  size, 
while  in  the  female  (No.  1008)  the  forward  wings  are 
vestiges  and  the  hinder  pair  have  wholly  disappeared. 

Among  the  more  generalized  Orthoptera  the  "  praying 
mantis"  (No.  ion,  egg-case;  Nos.  1012,  1013,  adults) 


METAZOA INSECTA.  415 

and  the  walking-stick  have  acquired  unique  specializa- 
tions. The  prothorax  of  the  adult  Stagmomantis  Carolina 
Linn.,  (Nos.  1012,  1013),  is  a  long,  slender  segment,  on 
the  forward  end  of  which  are  borne  the  extremely  large 
fore  legs  that  are  adapted  even  in  the  larval  state  for 
seizing  living  prey,  and  which  are  usually  raised  in  read- 
iness to  act  whenever  occasion  offers.  The  other  two 
pairs  of  legs  are  locomotor  organs  and  are  slightly 
modified.  The  wings  of  Mantis  are  too  small  to  be  of 
use,  and  the  motions  of  this  walking  type  are  extremely 
slow. 

Certain  species  of  Mantis  and  also  of  the  walking-stick 
(No.  1014,  Cythocrania  gigas)  have  remarkable  plant-like 
features  in  the  form  of  leaf-like  wings,  but  in  the  single 
species  found  in  New  England,  Diapheromera  femorata 
Say  (No.  1015),  the  wings  have  wholly  disappeared. 

These  insects  are  among  the  good  illustrations  of  what 
is  known  as  protective  coloration.  In  the  spring  time 
their  color  is  a  vivid  green,  but  as  autumn  approaches 
they  take  on  brownish  tints.  Whatever  may  be  the  cause 
of  these  changes,  whether  due  to  conscious  or  uncon- 
scious adaptation  of  the  insect  to  its  environment,  to  the 
direct  effects  of  heat  and  cold,  to  the  age  of  the  animal, 
or  to  some  unknown  cause,  they  certainly  render  the 
insect  less  conspicuous  and  in  this  way  serve  to  protect 
it  against  its  enemies.  One  of  the  most  remarkable  cases 
of  this  kind  is  seen  in  the  genus  Phyllium  (No.  1016, 
P.  scythe}.  The  anterior  wings  of  the  female  resemble 
leaves  and  their  hues  change  with  the  changing  seasons. 

Among  the  more  specialized  Orthoptera  are  the  Acridi- 
idae  or  locusts,  the  Locustidae  or  grasshoppers,  and  the 
Gryllidae  or  crickets. 

The  Acridiidae  are  good  type  forms  not  only  of  the 
Orthoptera  but  of  the  class  Insecta.  The  larva  (No. 
1017  ;  PI.  1018,  fig.  i)  possesses  the  similar  thoracic 
and  abdominal  segments  that  are  comparable  with  those 
of  the  Thysanura.  The  mouth  parts  are  the  same  in 


416  SYNOPTIC    COLLECTION. 

number  and  function  as  in  all  the  most  generalized 
groups,  but  the  running  type  of  insect  has  changed  into 
the  leaping  type,  and  this  is  true  not  only  of  the  adult 
but  also  of  the  young  larva. 

With  the  development  of  wings  the  pupa  (No.  1019, 
PI.  1018,  fig.  2)  takes  on  some  of  the  features  of  the 
adult.  The  first  thoracic  segment  becomes  differentiated, 
serving  to  protect  the  parts,  and  the  two  hinder  segments 
become  consolidated  until  in  the  adult  (No.  io2o,Me?an- 
oplus  femoratus  Scudd.,  $ ;  No.  1021,  ?;  PI.  1022,  fig. 
i,  side  view  of  $\  fig-  2,  dorsal,  with  view  of  dissection  of 
9  ),  they  are  so  complex  in  structure  that  it  is  difficult  to 
make  out  their  boundaries  with  absolute  certainty. 

The  abdomen  (PI.  1022,  figs,  i,  2)  retains  essentially 
its  primitive  simplicity,  though  a  fold  has  appeared  on 
either  side  above  which,  near  the  anterior  edge  of  the 
segment  are  situated  eight  pairs  of  spiracles,  while  there 
is  a  pair  in  each  of  the  posterior  segments  of  the  thorax 

(fig-  3). 

The  Acridiidae  have  a  tracheal  system  consisting  not 
only  of  air  tubes  but  also  of  a  large  number  of  air  sacs 
(fig.  3).  When  the  tubes  and  sacs  are  filled  with  air,  the 
body  is  greatly  lightened  and  the  insect  is  able  to  fly  con- 
siderable distances.  The  second  pair  of  wings  (fig.  2)  are 
most  useful  in  flight.  When  at  rest  these  organs  are 
folded  lengthwise  like  a  fan  and  lie  straight  with  the 
body ;  hence  the  name  of  Orthoptera  or  straight-winged 
insects.  The  hind  wings  are  often  large  and  handsomely 
colored,  as  in  one  of  our  largest  Locusts,  Dissosteira 
Carolina  Linn.  (No.  1023,  $  ;  No.  1024,  9  ,  with  wings 
spread). 

The  ovipositor  (PL  1022,  figs.  2,  3)  of  the  female  con- 
sists of  horny  spike-like  organs  situated  at  the  end  of 
the  abdomen  and  well  fitted  for  digging  holes  in  the  earth 
in  which  to  place  her  eggs. 

Most  of  the  parts  of  the  locust  exist  on  a  large  scale  in 
Dictyophorus  reticulatus  (No.  1025),  and  for  this  reason 


METAZOA INSECTA.  417 

the  genus  is  especially  helpful  to  teachers  and  students. 
The  wings  in  this  locust,  however,  are  useless  vestiges. 

One  of  the  interesting  specializations  occurring  among 
the  Acridiidae  is  in  the  case  of  the  grouse  locust,  Tettix, 
(No.  1026).  Here  the  prothorax  has  grown  backward, 
usurping  the  place  and  function  of  the  wing  covers, 
which,  no  longer  needed,  have  dwindled  to  tiny  rem- 
nants. 

The  Locustidae  are  represented  by  the  true  grasshop- 
per, Orchclimum  vulgare  Harris  (No.  1027).  It  lives  in 
grassy  meadows  and  fields,  and  is  a  vivid  green  in  color, 
while  the  katydid,  Cyrtophyllus  concavus  Say  (No.  1028), 
also  green  in  color,  frequents  trees  and  shrubs.  In  these 
insects  the  unconsolidated  condition  of  the  thorax  is 
correlated  with  the  weak  legs  and  wings.  The  latter 
organs  are  leaf-like  and  have  no  stiff  anterior  veins. 
In  the  katydid  the  forward  wings  are  so  large  and  con- 
cave that  they  encircle  the  posterior  part  of  the  body  like 
a  cylinder.  The  insect  opens  these  wings  suddenly  and 
brings  them  together  in  such  a  way  as  to  produce  the 
familiar  note  "Katydid,  she  did,  Katy  didn't."  The 
cone-headed  katydid,  Conocephalus  ensfger  Harris  (No. 
1029),  has  the  head  extending  forward  in  the  shape  of  a 
cone. 

The  female  of  Orchelimum  (No.  1027)  can  be  readily 
distinguished  from  the  male  by  the  sword-shaped  ovipos- 
itor. 

Among  the  specialized  Orthoptera  are  the  Gryllidae  or 
crickets.  The  body  in  both  the  larva  (No.  1030)  and  the 
adult  Gryllus  (No.  1031)  is  shortened  and  black  in  color. 
The  first  pair  of  wings  (No.  1031.)  are  small,  horny  wing 
covers,  while  the  second  pair  are  useless  in  flight.  The 
cricket  is  provided  with  an  ovipositor  and  a  pair  of  long 
cerci. 

A  remarkable  example  of  adaptation  of  structure  to 
habit  is  offered  by  the  mole  cricket,  GryllotaJpa  viilgaris 
Linn.  (No.  1032,  dorsal  and  ventral  side).  It  is  ex- 


418  SYNOPTIC   COLLECTION. 

tremely  interesting  to  note  that  before  the  first  moult  this 
insect  has  the  power  of  leaping  several  inches  l  but  after 
this  moult  it  is  more  sluggish.  Living  and  burrowing  in 
the  earth,  there  is  no  need  of  leaping  legs,  and  therefore 
these  have  become  essentially  like  the  second  pair. 

The  habit  of  excavating  tunnels  while  in  search  of 
food  has  modified  the  forward  legs  into  powerful  digging 
implements  which  are  seen  in  the  mature  larva  as  well  as 
in  the  adult.  This  same  habit  has  produced  a  similar 
structure  in  the  mole  of  the  Mammalia. 

Although  these  crickets  do  not  possess  the  power  of 
leaping  in  the  adult  stage,  they  can  swim,  and,  according 
to  Fletcher,2  "their  little  shining  black  eyes,  velvety  coats 
and  flexible  bodies  recall  strongly  the  appearance  of  the 
otter  particularly  when  emerging  from  the  water  or  crawl- 
ing over  stones." 


Order  8.  —  THYSANOPTERA. 

The  larva  (PI.  1033,  Parthenothrips  dracaenae  Heeg) 
of  the  Thysanoptera  has  the  general  features  of  the  Thy- 
sanura.  These  are  seen  still  more  plainly  in  Limothrips 
(=  Thrips)  tritici  Fitch  (PI.  1034,  fig.  i).  The  pupa 
(PI.  1033,  fig.  2),  however,  and  especially  the  adult 
(PI.  1033,  fig.  3,  and  PL  1034,  figs.  2,  3)  are  farther 
removed  from  their  own  larvae  than  the  adults  of  the 
Euplexoptera  or  the  Orthoptera.  The  mouth  parts  (PL 
1035,  %•  0  have  become  modified  for  sucking.  There  are 
still  three  pairs  of  these  organs  and  the  labrum  (fig.  2,0) 
but  the  mandibles  (fig.  .2,  b}  are  more  like  the  bristles  of 
the  Hemiptera,  the  next  order  to  be  described,  than  the 
horny  teeth  of  the  Orthoptera.  The  first  pair  of  maxillae 
(fig.  2,  c]  and  the  maxillae  of  the  second  pair,  which 

1Doran,  Can.  Ent.,  XXIV,  1892,  p.  271.' 
2  Can.  Ent.,  XXIV,  1892,  p.  25. 


METAZO  A I NSECTA .  419 

united  make  the  labium  (fig.  2,  d)<  are  very  unlike  the 
typical  mouth  parts  although  both  pairs  have  palpi  (see 
fig.  2,  c,  d}.  According  to  Osborne,1  the  Thripidae  are 
vegetable  feeders,  and  the  carnivorous  habit  when  pres- 
ent, as  in  Thrips  phylloxerae,  is  acquired  or  but  recently 
developed  in  the  species. 

The  beautiful  wings  with  their  long  delicate  fringe  (PI. 
1036,  Hcliothrips  haemorrhoidalis  Bouche)  have  given 
the  name  of  Thysanoptera  or  fringe-winged  insects  to  the 
order.  In  PI.  1034,  fig.  2,  these  wings  are  folded  over 
the  back. 

The  male  of  Limothrips  has  become  specialized  by 
reduction,  having  lost  its  wings  altogether  (see  PI.  1034, 
%.  3)- 


Order  9. —  HEMIPTERA. 

The  Hemiptera  have  probably  descended  from  some 
Campodea-like  ancestor,  though  many  of  the  stages  of 
descent  are  wholly  skipped  in  the  development  of  exist- 
ing forms.  Even  the  most  generalized  members  of  the 
order  are  far  removed,  as  regards  the  mouth  organs,  from 
the  Thysanura  and  also  from  the  orders  so  far  described. 

While  this  is  true,  there  are  nevertheless  certain  indi- 
cations here  and  there  that  the  sucking  apparatus  of  the 
Hemiptera,  which  is  so  perfect  in  most  of  the  members 
of  the  order,  is  an  adaptation  of  the  original  biting  mouth 
parts  of  the  ancestral  Thysanura.  For  instance,  in  the 
mouth  organs  of  Zaitha  (Z.  margineguttatd)  the  second 
pair  of  maxillae  which  form  the  sucking  tube  are  pro- 
vided with  palpi  (PI.  1037,  fig.  i).  These  have  also 
been  seen  in  Benacus  griseus  Say  (fig.  2),  Gem's  najas 
(fig.  3),  as  well  as  in  Nepa,  Ranatra,  and  Belostoma. 

As  we   already  know,  an   important  feature   of  biting 

1  U.  S.  Dep.  Agric.,  Insect  Life,  I,  no.  5,  1888,  p.  142. 


420  SYNOPTIC    COLLECTION. 

mouth  parts  is  the  possession  of  palpi,  and  the  discovery 
of  these  organs  by  Leon l  tends  to  confirm  his  statement 
that  there  is  a  complete  homology  between  the  Hemipter- 
ous  mouth  organs  and  those  of  biting  insects. 

The  Hemiptera  are  divided  into  two  groups,  the  Het- 
eroptera  and  the  Homoptera.  The  Heteroptera  are  the 
more  generalized,  inasmuch  as  they  have  more  direct 
development  than  the  Homoptera,  and  the  thoracic  and 
abdominal  regions  are  more  like  those  of  larval  cock- 
roaches. 

The  larvae  and  adults  of  some  of  the  water-inhabiting 
Hemiptera  bear  a  greater  resemblance  to  the  Thysanura 
in  the  general  proportions  of  the  body  than  do  the  terres- 
trial forms  like  the  typical  Anasa  or  squash-bug.  For 
this  reason  they  will  be  considered  first. 

The  generalized  characters  of  Notonecta  are  seen  in 
the  larva.  Besides  these  both  the  larva  and  the  adult 
(No.  1038)  possess  adaptive  features  fitting  them  for 
aquatic  life.  The  back  is  shaped  somewhat  like  the  bot- 
tom of  a  boat  and  the  insect  swims  with  it  downward 
hence  the  name  of  back- swimmer.  The  hind  pair  of  legs 
have  become  efficient  oars  ;  concomitantly  their  structure 
has  changed  and  they  have  become  long,  flattened  organs 
fringed  with  hairs. 

The  water-inhabiting  Hemiptera,  like  all  water  insects, 
breathe  air.  Notonecta  often  comes  to  the  surface  and 
stows  away  a  supply  under  its  wings,  while  another  water 
boatman,  Corixa  (No.  1039),  is  enveloped  in  a  film  of  -air 
which  gives  it  a  silvery  appearance. 

The  largest  Hemipterous  insect  is  the  giant  water-bug, 
Belostoma  americanum  (No.  1040,  dorsal  and  ventral 
side),  which  on  account  of  its  size  is  particularly  helpful 
to  the  student. 

The  segments  of  the  thorax  in  this  insect  are  free  like 
those  of  the  abdomen.  The  head  is  flat  and  placed  hori- 

1  Zool.  Anz.,  XX,  1897,  p.  73. 


METAZOA INSECTA.  421 

zontally ;  the  antennae  are  concealed  from  view,  being 
hidden  under  the  eyes.  The  jointed  sucking  tube  ex- 
tends backward  and  consists  of  the  two  parts  of  the  sec- 
ond pair  of  maxillae  united.  Within  this  tube  are  the 
mandibles  and  first  pair  of  maxillae,  which  are  sharp 
bristle-like  organs  used  for  piercing  the  flesh  of  animals. 
The  legs  are  greatly  modified ;  the  forward  pair  are  pro- 
vided with  claws,  one  jaw  of  which  closes  upon  the  other 
like  the  blade  of  a  knife  upon  its  handle.  These  legs  are 
strong  enough  to  catch  small  fish  and  to  hold  them,  while 
the  sucking  tube  draws  the  blood  of  the  animal.  The 
hind  legs  are  powerful  swimming  organs.  The  anterior 
pair  of  wings  exhibit  the  peculiar  structure  of  the  typical 
Hemipterous  wing,  having  a  horny  basal  portion,  while 
the  remaining  part  is  membranous ;  hence  the  name 
Hemiptera,  meaning  half  and  wing.  The  posterior  wings 
are  membranous  throughout,  and  are  useful  flying  or- 
gans ;  both  pairs  of  wings  lie  flat  on  the  body,  their  tips 
crossing.  When  wings  are  present  in  these  water  insects, 
they  aid  in  seeking  out  a  favorable  habitat  for  the  dis- 
semination of  the  species ;  Belostoma  is  capable  of  long 
sustained  flights,1  and  Zaitha  (Nos.  1041,  1042)  resem- 
bles Belostoma.  Zaitha  has,  however,  the  habit  of  fasten- 
ing its  eggs  on  its  back  (No.  1041).  According  to  Slater,2 
it  is  the  male  that  carries  the  eggs,  and  the  ovipositor  of 
the  female  is  too  short  to  place  the  eggs  on  her  back,  as 
has  been  supposed.  The  wing  covers  are  concealed,  as 
seen  in  No.  1041,  so  that  these  organs  are  useless  for 
locomotion  until  the  youn'g  are  hatched. 

The  spiracles  in  Belostoma  and  Zaitha  are  apparently 
closed,  but  they  have  valvular  openings  which  admit  the 
air. 

Ranatra  (No.  1043)  has  besides  the  spiracles  a  pair  of 
respiratory  tubes  at  the  end  of  the  abdomen.  This  insect 

1  Dimmock,  Ann.  Rep.  Fish  and  Game  Comm.  Mass.,  1886,  p.  70. 
1  Amer.  Nat.,  XXXIII,  1899. 


422  SYNOPTIC   COLLECTION. 

has  a  long  body  and  long  legs  like  the  walking-stick  of 
the  Orthoptera,  and  the  wings  are  reduced  in  size,  while 
in  Hygrotrechus  (No.  1044),  an  insect  that  lives  on  the 
surface  of  the  water,  the  wings  have  disappeared. 

In  striking  contrast  to  these  long-bodied  and  long- 
legged  Hemiptera  is  the  Galgulus  oculatus  Fabr.  (No. 
1045),  which  inhabits  marshes.  On  account  of  its  short, 
broad  body  and  projecting  eyes  it  is  often  called  the 
toad-shaped  bug.  It  is  a  good  leaper  and  its  color  har- 
monizes with  its  surroundings. 

The  terrestrial  Hemiptera  are  well  represented  by  the 
squash-bug,  Anasa  tristis  De  Geer  (No.  1046,  eggs,  larva, 
pupa,  adult;  No.  1048,  adult).  In  the  larva  (No.  1046; 
PL  1047,  &£•  I)  tne  thoracic  segments  are  unequal  in 
size,  although  they  are  freely  movable.  The  head,  an- 
tennae, and  legs  are  dark-colored,  presenting  a  striking 
contrast  to  the  light-colored  body  and  indicating  that 
these  appendages  perform  hard  labor.  The  posterior 
lateral  angles  of  the  mesothorax  and  metathorax  grow 
out  (No.  1046)  until  the  distinct  wing  pads  of  the  pupa 
(No.  1046  ;  PI.  1047,  fig.  2)  are  formed.  One  can  often 
find  all  the  stages  of  the  developing  wings  in  the  squash- 
bugs  that  infest  a  single  plant. 

The  prothorax  in  the  adult  (Nos.  1046,  1048  ;  PI.  1047, 
fig-  3>/)  has  grown  backward  and  covered  the  larger 
part  of  the  mesothorax,  which  is  also  seen  in  PL  1047, 
fig.  4,  where  the  prothorax  (p)  is  raised  exposing  the 
mesothorax  (ms) ;  the  latter  is  large  and  its  posterior  part, 
the  scutellum,  conceals  the  dorsal  part  of  the  small  nar- 
row metathorax  (fig.  3,  mf).  , 

The  jointed  sucking  tube  (fig.  3,  su\  No.  1048,  with 
tube  extended)  is  essentially  the  same  in  the  larva  and 
adult.  It  is  seen  in  fig.  5,  where  the  bristle-like  mandi- 
bles and  maxillae  are  drawn  out  of  the  tube  or  second 
pair  of  maxillae  (fig.  5,  mx"). 

The  distinctive  characters  of  the  wings  of  Anasa  and 
of  the  Heteroptera  generally  are  well  seen  in  fig.  3.  The 


METAZOA INSECTA.  423 

basal  portion  is  chitinous  and  has  few  veins,  while  the 
terminal  part  is  membranous  and  is  richly  supplied  with 
veins.  The  under  wings  (fig.  3,  w")  are  membranous 
throughout  but  have  few  veins.  Both  pairs  of  wings  lie 
flat  upon  the  back  and  their  tips  overlap. 

Peculiar  specializations  are  found  in  many  of  the  adult 
Heteroptera,  the  reasons  for  which  are  not  always  known, 
owing  chiefly  to  the  fact  that  much  information  in  regard 
to  the  habits  of  the  insects  is  wanting. 

The  thread-legged  bugs  like  Emesa  (No.  1049)  have 
the  habit  of  hanging  to  twigs  by  their  long  legs  and 
swinging  backward  and  forward.  The  fore  legs  are  pro- 
vided with  claws  for  seizing  their  prey  and  are  well  fitted 
for  this  purpose. 

Especially  attractive  is  the  lace-bug,  Corythuca  arcuata 
Say  (No.  1050).  This  insect  lives  on  the  under  side  of 
oak  leaves  where  its  eggs  (PL  1051,  fig.  i)  are  laid.  The 
larva  (fig.  2)  has  such  a  spiny  thorax  and  abdomen  that 
it  looks  like  "a  lobe  of  a  prickly  cactus"  (Comstock). 
The  adult  (fig.  3)  is  distinguished  from  other  insects  by 
the  exquisite  gauzy  appearance  of  the  body.  This  is  due 
to  the  wing  covers  that  are  formed  of  a  nearly  transpar- 
ent membrane  netted  with  veins. 

Prionidus  cristatus  Linn.,  or  the  wheel-bug  (No.  1052) 
destroys  great  numbers  of  caterpillars  and  other  insects. 
Both  as  larva  and  adult  it  is  a  hardy,  rapacious  creature, 
and  it  may  be  that  the  cog-wheel  crest  of  the  thorax  (No. 
1052)  gives  strength  to  the  animal  when  making  its 
attacks. 

In  Scutellera  (No.  1053)  the  scutellum  of  the  meso- 
thorax  has  developed  for  some  reason  so  that  it  covers 
both  pairs  of  wings  and  resembles,  at  first  sight,  the  horny 
wing  cases  of  the  beetles. 

Among  the  more  specialized  Heteroptera  is  the  bed-bug, 
Acanthia  lectularia  (No.  1054  ) .  It  is  adapted  to  its  hab- 
itat by  having  a  flattened  body,  strong  mouth  parts,  and 
a  thorax  that  is  almost  entirely  unencumbered  by  wings. 


424  SYNOPTIC    COLLECTION. 

The  prothorax  is  of  good  size  and  aids  the  head  and 
mouth  organs,  but  the  mesothorax  is  reduced  in  size  and 
bears  the  tiny  scales  which  will  probably  in  time  wholly 
disappear,  while  the  metathorax  is  already  a  vestige  with- 
out appendages. 

Most  specialized  of  all  the  Heteroptera  are  the  parasi- 
tic lice.  Here  the  thoracic  segments  are  fused  together 
and  even  the  sutures  are  indistinct  (PL  1055,  the  body 
louse,  Pediculus  vestimenti  Nitzsch  ;  hair  line  indicates 
natural  size)  or  apparently  wanting  (PI.  1056,  the  swine 
louse,  Haematopinus  suis  Leach)  until  brought  out  by 
staining  reagents.  When  thus  brought  into  view,  they 
are  proofs  of  the  evolutionary  history  through  which  these 
parasites  have  passed  and  demonstrate  that  the  position 
of  these  insects  in  a  natural  classification  must  be  with 
the  secondary  and  specialized  forms.  Associated  with 
this  specialization  of  the  thorax  is  the  loss  of  compound 
eyes  and  the  absence  of  both  pairs  of  wings.  The  suck- 
ing tube  has  lost  its  joints,  is  fleshy  and  capable  of  exten- 
sion by  rolling  inside  out.  The  feet  have  ceased  to  be 
running  or  leaping  organs,  but  are  provided  with  claws 
for  climbing  upon  hairs  or  for  clinging  to  the  flesh  of  the 
host. 

The  generalized  Homoptera  are  represented  by  the 
Cicadidae.  The  seventeen-year  species,  Tibicen  septende- 
fim  Linn.,  often  called  cicada  (PI.  1057,  larva;  No. 
1058,  adult),  requires  that  period  of  time  for  its  develop- 
ment in  the  north,  and  thirteen  years  in  the  south  ;  Cicada 
marginata  Say,  (No.  1059,  pupa  skin;  No.  1060,  ^ ;  No. 
1 06 1,  9  )  probably  develops  in  a  shorter  time,  while  our 
common  dog-day  cicada,  C.  canicularis  Harr.  (PL  1062, 
probably  larva ;  No.  1063,  pupa  skin  and  adult)  reaches 
the  adult  stage  in  two  years  (Comstock).  There  is  little 
in  the  larva  of  this  insect  that  suggests  the  Thysanuran 
stock  form,  although  in  certain  characters  the  larva  of  the 
seventeen-year  cicada  when  newly  hatched  (PL  1057, 
fig.  i)  approaches  the  Thysanura  nearer  than  the  proba- 


METAZOA  — INSECT  A.  425 

ble  larva  of  the  two-year  cicada  (PL  1062).  The  resem- 
blance is  seen  especially  in  the  similarity  of  the  thoracic 
segments. 

At  the  time  of  hatching,  the  fore  legs  are  fitted  for 
burrowing  (PI.  1057,  fig.  i),  having  strong  digging  claws 
at  their  ends.  These  are  needed  when  the  larvae,  which 
hatch  from  eggs  laid  in  the  branches  of  trees,  drop  to  the 
ground  and  begin  to  burrow  downward  to  the  roots. 
Development  is  so  extremely  slow  that  in  six  years  the 
larva  of  the  seventeen-year  species  has  hardly  attained 
one  fourth  its  full  size  (Riley).  There  are  probably 
twenty-five  or  thirty  moults,  the  body  gradually  short- 
ening, thickening,  and  growing  darker  with  age. 

The  larva  lives  on  the  sap  of  roots  and  the  moisture  in 
the  earth,  which  it  takes  by  means  of  its  strong  sucking 
tube.  Much  of  the  time  it  lies  in  an  oval  cell  which  it 
has  made  for  itself  by  using  its  claw  as  one  would  use  a 
pick.  It  never  passes  into  a  quiescent  pupal  stage  in 
which  structural  changes  are  gone  through  quickly; 
nevertheless,  it  lies  in  a  cell,  as  we  have  said,  and  is  able 
to  live  a  considerable  time  without  taking  nourishment. 
In  these  ways  it  approaches  pretty  closely  to  the  quies- 
cent condition  of  the  more  specialized  insects.  Gradu- 
ally wing  pads  are  developed  and  the  pupa  (PI.  1057, 
fig.  2)  works  its  way  to  the  surface.  "To  witness  these 
pupae  in  ....  vast  numbers  ....  swarming  out  of  their 
subterranean  holes  and  scrambling  over  the  ground,  all 
converging  to  the  one  central  point,  and  then  in  a  steady 
stream  clambering  up  the  trunk  and  diverging  again  on 
the  branches,  is  an  experience  not  readily  forgotten  and 
affording  good  food  for  speculation  on  the  nature  of 
instinct.  The  phenomenon  is  most  satisfactorily  wit- 
nessed where  there  is  a  solitary  or  isolated  tree."  *  In 
about  an  hour  after  rising  and  settling,  the  transformation 

1  Riley,  Rep.  of  the  Entomologist,  U.  S.   Dep.  Agric.,  1885,  p. 

237- 


426  SYNOPTIC    COLLECTION. 

begins,  and  usually  several  hours  pass  before  the  insect 
is  ready  for  its  aerial  life.  It  is  to  be  noticed  that  during 
the  transforming  process  the  wings  lie  flat  on  the  back 
before  they  slope,  roof-like,  at  the  sides. 

The  development  of  our  species  of  cicada  is  acceler- 
ated so  that  it  is  accomplished  in  twg  years.  The  larva 
has  a  shortened  cylindrical  body  like  a  grub.  The  seg- 
ments of  the  thorax  are  unequal  in  size,  the  metathorax 
being  much  narrower  than  the  prothorax  or  mesothorax, 
and  the  segments  of  the  abdomen  are  tapering. 

The  fore  wings  of  the  adult  cicada  and  of  all  Homop- 
tera  differ  from  those  of  the  Heteroptera  in  being  mem- 
branous throughout,  as  seen  in  Nos.  1058,  1060,  1063. 
The  adult  male  produces  the  shrill  piercing  note  so  often 
heard  in  July  and  August.  This  sound  is  made  by 
means  of  two  "  drums  "  on  the  lower  side  of  the  basal 
part  of  the  abdomen.  These  drums  are  covered  by  flaps 
which  are  much  larger  in  the  male  (No.  1060)  than  in 
the  female  (No.  1061).  In  Cicada  tibicen  Linn.  (— pru- 
inosa  Say)  (No.  1064)  there  is  a  white  pubescence  on 
the  lower  side. 

The  Homoptera  include  insects  that  have  become 
modified  in  most  peculiar  ways.  For  instance  in  the 
lantern  fly,  Fulgora,  (No.  1065)  the  forward  part  of  the 
head  is  greatly  enlarged  and  extends  in  front,  forming  a 
rostrum  which  is  luminous  at  night.  A  nearly  related 
form,  Hotinus,  (No.  1066)  is  armed  on  the  head  with  a 
long  curved  horn,  which  appears  to  be  an  organ  of  of- 
fence and  defence. 

The  most  specialized  of  the  Hemiptera  are  the  Aphi- 
des (No.  1067,  Aphis)  and  the  scale  insects  or  Coccidae. 
The  life  history  of  the  hop-plant  aphis,  Phorodon  humuli 
Schrank,  has  been  worked  out  more  fully  than  that  of 
many  species. 

Whether  we  begin  with  the  fertilized  egg  or  with  the 
sexually  mature  male  and  female,  we  are  dealing  with 
specialized  conditions,  since  in  this  Aphid  the  fertilized 


METAZOA INSECTA.  427 

egg  develops  into  a  form  far  removed  from  its  parents 
and  from  the  ancestral  Hemiptera,  while  the  apparently 
normal  sexually  mature  male  and  female  develop  from 
the  unfertilized  eggs  of  agamic  individuals. 

The  unfertilized  eggs  may  be  in  a  certain  sense  her- 
maphroditic, but  without  going  into  a  discussion  l  of  the 
subject  of  parthenogenesis,  or  the  development  of  living 
organisms  independently  of  the  male,  it  is  evident  that 
the  sexually  mature  male  and  female  which  pair  and  give 
rise  to  fertilized  eggs  are  nearer  the  primitive  insects, 
and  also  the  ancestral  forms  of  nearly  all  the  groups 
above  the  Protozoa,  than  the  exceptional  agamic  forms 
which  bring  forth  living  young.  In  the  latter  case 
acceleration  in  development  has  caused  the  embryonic 
and  larval  stages  to  be  passed  within  the  body  of  the 
parent,  and  the  young  when  born  may  be  compared  to 
active  pupae  which  are  so  specialized  .  that  they  never 
acquire  wings,  but  in  a  few  days  are  mature  insects  and 
ready  in  their  turn  to  bring  forth  living  Aphides. 

Unfortunately,  a  figure  of  the  larva  of  the  male  Phoro- 
don  cannot  be  given,  but  the  pupa  (PI.  1068,  fig.  i)  has 
the  rudiments  of  wings  like  the  pupae  of  most  insects. 
These  pupae  develop  into  the  male  (fig.  2)  which  has  two 
pairs  of  wings,  although  the  posterior  pair  are  small  in 
size.  The  sexually  mature  female  is  more  specialized 
than  the  male,  inasmuch  as  it  never  possesses  wings. 
Its  young,  which  is  probably  the  specialized  wingless 
pupa,  is  seen  in  fig.  3  ;  the  adult  with  the  body  distended 
with  eggs  is  represented  in  fig.  4  and  with  the  body 
shrunken  during  egg-laying  in  fig.  5. 

These  fertilized  eggs  are  laid  upon  the  branches  of 
plum  trees.  Each  develops  into  a  wingless  female  often 
called  the  "stem  mother"  (fig.  6),  which  in  a  few  days 
produces  living  young,  entirely  independent  of  the  male. 
This  second  generation  (fig.  7)  gives  rise  in  the  same 

1  See  Weismann,  Brooks,  Geddes,  Adler. 


428  SYNOPTIC    COLLECTION. 

way  to  a  third  generation  (fig.  8,  pupa  ;  fig.  9,  adult), 
but  these  are  winged  agamic  females.  These  "winged 
migrants  "  fly  from  the  plum  tree  to  the  hop  plant.  The 
fourth  generation  or  the  first  on  the  hop  plant  is  repre- 
sented in  the  act  of  crawling  in  fig.  10.  Several  genera- 
tions may  be  produced  parthenogenetically  on  the  hop 
vine,  fig.  1 1  representing  the  normal  parthenogenetic 
female  of  the  sixth  generation.  In  the  autumn,  winged 
females  (fig.  12,  pupa;  fig.  13,  adult)  are  again  devel- 
oped and  these  "return  migrants"  fly  back  to  the  plum. 
They  are  agamic  and  soon  produce  young  which,  how- 
ever, develop  into  the  sexual  wingless  females  already 
described.  Later  the  winged  males  appear  and  sexual 
reproduction  follows. 

This  remarkable  specialization  in  development  is  cor- 
related with  specialized  structures  and  with  social  habits. 
The  thoracic  segments,  which,  generally  speaking,  are 
distinct  in  the  Hemiptera,  are  more  or  less  fused  together 
in  these  forms ;  especially  is  this  the  case  with  the 
mesothorax  and  metathorax,  the  boundaries  of  which  are 
difficult  to  make  out. 

The  dorsal  tubes  on  the  abdomen  of  both  the  sexual 
and  the  parthenogenetic  forms  which  discharge  the  sweet 
liquid,  "honey  dew,"  is  a  unique  adaptation  on  the  part 
of-the  Aphides  which  brings  them  into  harmonious  rela- 
tions with  other  insects  that  are  remotely  connected  with 
them  genetically,  such  as  ants. 

The  grape  aphis,  Phylloxera  vastatrix  Planchon,  has 
carried  specialization  so  far  that  there  are  several  phases 
or  types  of  the  species,  and  it  is  probable  that  in  one 
type,  Gallaecola  or  the  gall-inhabiting  form,  the  male  has 
ceased  to  exist. 

According  to  Riley *  the  first  galls  that  appear  on  the 
grape  leaves  in  the  spring  time  are  formed  mainly  by 
young  Phylloxera  that  hatch  on  the  roots  of  the  grape 

X6th  Ann.  Rep.  Nox.  and  Benef.  Insects  Mo.,  1874,  p.  37. 


METAZOA INSECTA.  429 

vine.  We  will  therefore  begin  with  the  root-inhabiting 
type  or,  as  it  is  called,  the  Radicicola.  This  type  pro- 
duces two  forms,  the  sexually  mature  winged  form  and 
the  parthenogenetic  or  wingless  form.  Since  the  sexually 
mature  form  is  nearer  the  ancestral  type  than  the  reduced 
parthenogenetic  form,  we  will  consider  it  first.  Its  larva 
(PI.  1069,  fig.  i)  has  distinct  tubercles;  it  develops 
into  the  pupa  (fig.  2,  dorsal  view;  fig.  3,  ventral  view), 
which  crawls  to  the  surface  of  the  ground  and  in  sum- 
mer transforms  into  the  winged  insect  (fig.  4,  dorsal 
view;  fig.  5,  ventral  view).  These  winged  forms  are 
mostly  females.  Among  them  is  a  smaller,  shorter  form 
(fig.  6)  which  may  be  the  male,  although  this  is  not  proved. 
The  winged  females  lay  from  two  to  five  eggs  above 
ground  and  die  on  the  approach  of  winter.  Their  eggs 
live  through  the  winter  and  in  the  spring  the  larvae  climb 
to  the  leaves  of  the  vine  and  there  make  galls.  Since, 
however,  most  of  the  galls  are  made  by  the  second  or 
parthenogenetic  form  of  the  Radicicola,  we  will  describe 
it  next.  Its  larva  (fig.  7)  which  is  at  first  without  tuber- 
cles, develops  them  later,  as  seen  in  fig.  8,  dorsal  view ; 
fig.  9,  side  view.  This  form,  however,  never  acquires 
wings  and  as  it  grows  it  becomes  more  specialized  by 
reduction  ;  it  hibernates  in  the  larval  state,  but  when  the 
sap  starts  in  the  spring,  it  matures  and  lays  parthenoge- 
netic eggs  which  develop  into  wingless  females.  It  is 
chiefly  these  females  that  give  rise  to  the  gall-inhabiting 
type  or  the  Gallaecola.  They  make  their  way  out  of  the 
earth  and  to  the  leaves  of  the  vine  which  they  pierce  on 
the  lower  side,  thereby  causing  the  formation  of  abnormal 
growths  or  galls.  The  eggs  are  laid  in  these  galls.  They 
hatch  into  plump,  six-legged  larvae  (fig.  10,  dorsal  view; 
fig.  n,  ventral  view)  which  leave  the  gall  and  find  their 
way  to  the  leaves  of  the  vine.  These  they  in  their  turn 
pierce  and  the  resultant  gall  becomes  the  home  of  the 
adult  (fig.  12,  dorsal  view;  fig.  13,  ventral  view;  fig.  14, 
side  view).  In  this  situation  the  antennae  and  legs 


430  SYNOPTIC    COLLECTION. 

become  reduced  in  size.  The  body  distends  with  unfer- 
tilized or  parthenogenetic  eggs.  These  are  laid  until  the 
gall  is  crowded,  the  mother  shriveling  in  the  process,  and 
dying  at  its  termination.  Five  or- six  generations  are 
produced  parthenogenetically  during  the  summer  and  the 
number  of  individuals  born  is  enormous.  Since  each  in- 
dividual repeats  the  process  of  making  its  gall-home  and 
filling  it  with  eggs,  the  number  of  galls  is  also  very  large. 
With  the  fall  of  the  leaves  in  the  autumn,  the  Gallaecola 
that  remain,  quit  the  vines  and  finding  their  way  to  the 
roots  of  the  grape  become  Radicicola.  It  is  interesting 
to  note  that  the  newly  hatched  larvae  which  develop  from 
the  eggs  of  the  root-inhabiting  type  cannot  be  distin- 
guished from  those  of  the  gall-inhabiting  type  (compare 
fig.  7  with  fig.  10),  but  in  time  the  former  develop  tuber- 
cles, as  already  stated,  and  the  two  types  become  distinct, 
although  so  closely  connected  genetically  that  they  are 
one  and  the  same  species. 

We  have  here  apparently  the  unusual  phenomenon  of 
parthenogenetic  individuals  of  two  different  types  carry- 
ing on  the  principal  role  in  the  life  history  of  a  spe,cies, 
and  the  sexual  females  and  possible  males  playing  such 
an  unimportant  part  that  it  seems  as  if  they  could  be 
dispensed  with  altogether.  It  may  be,  however,  that  the 
"problematical  male"  (fig.  6)  is  more  necessary  for  the 
continuance  of  the  species  than  it  appears,  or  possibly 
Phylloxera  has  "a  true  sexed  generation  of  minute,  wing- 
less "  forms,  as  in  the  wooly  aphis  (Schizoncura  lanigera 
Hausmann) ,  of  the  apple.1 

In  one  important  structural  feature  Phylloxera  differs 
from  the  hop-plant  aphis:  it  never  secretes  "honey  dew," 
and  consequently  is  without  the  honey  tubes. 

The  Coccidae  or  scale  insects  are  in  certain  ways 
unique  among  insects.  The  newly  hatched  larva  of  the 

1  Marlatt,  U.  S.  Dep.  Agric.,  Div.  Ent.,  Circular  no.  20.  ser.  2, 
1897,  p.  3. 


METAZOA INSECTA.  431 

female  cottony  cushion-scale,  Icerya  purchasi  Maskell  (PI. 
1070,  fig.  i,  dorsal  side;  fig.  2,  lower  side,  colored  from 
life),  has  club-shaped  antennae  each  bearing  four  long 
hairs.  It  would  be  interesting  to  know  the  cause  of  the 
elaborate  development  of  these  organs.  The  eyes  are 
situated  on  the  margin  of  the  head  (see  fig.  2)  and  are 
raised  on  short  tubercles.  There  are  rows  of  pores  and 
many  hairs  on  the  body.  In  the  second  stage  (fig.  3) 
and  also  the  third  (fig.  4)  the  antennae  are  shortened,  and 
the  eyes  are  no  longer  on  the  margin  but  on  the  ventral 
side  of  the  head.  The  pores  and  hairs  are  scattered 
irregularly  over  the  body.  The  adult  female  (fig.  5,  dor- 
sal view)  is  provided  with  tufts  of  black  hairs  around  the 
edge  and  with  an  immense  number  of  pores.  The  wax 
filaments"  that  issue  from  the  pores  are  curly.  Besides 
these  wax  threads  the  animal  produces  glassy-like  fila- 
ments and.  from  one  large  pore  in  the  back  globules  of 
honey  dew  are  ejected.  When  ready  to  lay  her  eggs,  the 
female  lies  flat  on  the  back,  the  edges  of  the  body  turned 
slightly  upward,  and  the  waxy  material  of  which  the  sac 
is  composed  begins  to  issue  from  countless  pores  on  the 
under  side  of  the  body,  but  more  especially  along  the 
sides  below.  As  the  secretion  advances,  the  body  is 
raised,  the  forward  end  being  still  attached,  until,  near 
the  completion  of  the  sac,  the  insect  is  apparently  stand- 
ing on  its  head  nearly  at  right  angles  to  the  surface  of 
attachment  (fig.  6,  dorsal  view  ;  fig.  7,  side  view,  showing 
the  pale  greenish  gray  form,  and  with  part  of  the  white 
egg  covering  torn  away,  showing  the  eggs  stained  with 
carmine) .  The  egg-laying  begins  as  soon  as  a  thin  layer 
of  the  secretion  has  formed  on  the  under  side  of  the  abdo- 
men, and  it  continues  during  the  formation  of  the  sac 
(Riley).  The  egg-sac  is  snowy  white,  in  striking  contrast 
with  the  reddish  colored  insect.  From  the  middle  of  the 
under  side  of  the  sac  the  larvae  make  their  escape  soon 
after  hatching. 

The  male  is  less   specialized  by   reduction  than    the 


432  SYNOPTIC    COLLECTION. 

female,  inasmuch  as  it  passes  through  a  normal  larval, 
pupal,  and  winged  adult  stage,  but  it  is  more  specialized 
by  having  a  quiescent  pupal  stage  and  an  indirect  develop- 
ment unlike  any  of  the  insects  in  the  large  group  of 
Insecta  including  orders  1-9,  which  we  have  been  describ- 
ing. The  quiescent  pupa  (fig.  8)  is,  in  fact,  here  met  for 
the  first  time,  as  is  also  its  covering  or  cocoon  (fig.  9), 
which  in  this  case  is  made  of  wax  so  that  it  melts  readily 
when  heat  is  applied. 

Associated  with  this  specialization  in  development  there 
is  the  loss  of  mouth  parts  in  the  adult  male  (fig.  10),  and 
the  reduction  of  the  second  pair  of  wings  to  organs  that 
resemble  the  halteres  or  balancers  of  the  Diptera,  the 
most  specialized  order  of  the  class  of  Insecta. 


Order  10.  —  COLEOPTERA. 

» 

The  more  generalized  members  of  the  Coleoptera  have 
larval  characters  in  common  with  the  Thysanura,  while 
the  adults  are  similar  in  certain  features  to  the  Enplexop- 
tera,  Orthoptera,  and  Hemiptera.  The  most  specialized 
Coleoptera,  on  the  other  hand,  have  lost  completely  the 
larval  Thysanuriform  characters  and  the  adults  are  far 
removed  from  their  generalized  ancestors. 

For  the  sake  of  clearness  we  will  consider,  first,  those 
beetles  whose  larvae  resemble  more  or  less  the  Thysanura  ; 
secondly,  those  which  have  larvae  in  the  form  of  soft, 
cylindrical,  and  active  grubs,  possessing  three  pairs  of 
feet ;  thirdly,  those  whose  larvae  are  elongated,  with  min- 
ute feet,  suggesting  in  their  general  aspect  the  caterpillars 
of  the  more  specialized  order,  the  Lepidoptera;  and, 
fourthly,  those  whose  grub-like  or  caterpillar-like  larvae 
have  become  specialized  by  reduction,  so  that  they  are 
soft,  cylindrical  and  inactive,  having  only  vestiges  of  feet, 
or  in  some  cases  being  wholly  without  these  organs. 

This  arrangement  not  only  holds   good  for  the  order 


METAZOA INSECTA.  433 

but  in  some  of  the  families,  the  Chrysomelidae  for 
instance,  the  Thysanuriform,  grub,  and  caterpillar-like 
larvae  can  all  be  found. 

Many  of  the  Carabidae  or  ground  beetles  have  elon- 
gated, chitinous,  more  or  less  flattened  larvae.  The  body 
is  of  nearly  equal  breadth  throughout  and  the  segments 
are  distinct. 

The  Thysanuriform  characters  are  plainly  seen  in  Pat- 
robus  longicornis  Say  (PI.  1071),  although  the  adult  (No. 
1072)  has  become  specialized  by  the  loss  of  its  second 
pair  of  wings. 

Calosoma  is  another  Carabid  whose  larva  is  elongated 
but  more  plump  in  aspect  than  that  of  Patrobus.  The 
pupa  has  its  parts  free,  while  the  adult  (No.  1073,  C.  scru- 
tator} is  a  brilliant  beetle  with  well  developed  wings. 
%  The  Coccinellidae  or  lady-birds  are  similar  to  the  Car- 
abidae in  many  respects  and  they  too  have  elongated 
Thysanuriform  larvae  (PI.  1074,  fig.  i,  Coccinella  novemno- 
tata  Herbs.).  These  larvae  fasten  themselves  by  the 
posterior  end  of  the  body  and  develop  into  pupae  (fig.  2, 
with  the  larval  skin  attached  at  the  anal  end).  The  pupae 
are  often  brightly  colored  as  well  as  the  adults  (No.  1075, 
dorsal  side  ;  No.  1076,  ventral  side;  PI.  1074,  fig.  3),  which 
in  this  species  have  nine  spots.  Sometimes  the  adult  in 
this  family  has  a  uniform  color  and  a  fine  pubescence  of 
short  hairs,  as  seen  in  Scymnus  punctum  LeC.  (PI.  1077, 
figs,  i,  2,  3,  larva,  pupa,  and  adult),  a  shining  black  Coc- 
cinellid  with  yellow  antennae.  These  beetles  are  not  only 
extremely  pretty  insects  but  they  are  also  extremely  useful 
in  devouring  pests  such  as  Phylloxera  and  the  like. 

The  fast-running  tiger  beetles  of  the  Cicindelidae  have 
Thysanuriform  larvae  which,  however,  are  peculiarly  mod- 
ified by  habit.  These  larvae  live  in  holes  and  while  there 
catch  their  prey.  For  this  purpose  the  head  is  large  and 
strong,  the  mandibles  long  and  curved,  while  two  tuber- 
cles on  the  abdomen,  each  with  a  recurved  hook,  hold  the 
insect  in  any  part  of  its  burrow.  The  adults  (No.  1078, 
Cicindela  sexguttata)  are  often  brilliant  in  coloring. 


434  SYNOPTIC    COLLECTION. 

The  larva  of  Amphizoa  lecontei  Matth.,  (PI.  1079,  fig.  i, 
dorsal  view;  fig.  2,  ventral  view)  is  Thysanuriform  in 
general  aspect  and  is  strongly  chitinous  above.  When 
the  larva  is  extended,  the  body  is  much  longer  and  resem- 
bles the  larvae  of  the  Carabidae.  The  larva  and  adult 
live  along  the  sides  of  rapid  mountain  streams,  floating  on 
sticks  in  eddies  or  crawling  among  stones.  "  It  gives  the 
impression,"  says  Hubbard,1  "of  a  terrestrial  beetle  with 
amphibious  or  semiaquatic  habits." 

Dytiscus  is  a  water  beetle  whose  larvae  (PI.  1080,  fig. 
i,  D.  marginal^  Ahr.)  breathe  by  means  of  two  spiracles 
at  the  end  of  the  abdomen.  The  air  is  taken  in  at  the 
surface  of  the  water,  as  is  also  the  case  with  the  adult 
(No.  1081,  D.  verticalis  Say,  dorsal  side;  No.  1082,  ven- 
tral side)  which  stores  its  air  away  under  the  wing  covers. 

The  larva  is  remarkable  for  having  primarily  so]jd 
mandibles  modified  into  hollow  organs  (PI.  1080,  fig.  2, 
showing  the  opening  at  the  smaller  end)  through  which 
the  juices  of  its  prey  are  sucked.  Here,  then,  we  have 
a  mandibulate  type  of  insect  converted  into. a  suctorial 
type. 

The  Gyrinidae  are  also  aquatic  beetles  in  both  the  lar- 
val and  adult  states,  and  possess  other  specializations  for 
such  a  habitat.  Along  each  side  of  the  abdominal  seg- 
ments of  the  larva  (PI.  1083,  Orectochilus  villosus  O.  F. 
Mull.)  there  are  branchial  organs  used  for  respiration  and 
locomotion.  The  adults  (No.  1084,  Gyrinus)  are  usually 
seen  upon  the  surface  of  the  water  swimming  by  means 
of  their  paddle-like  feet.  They  are  provided  with  a  pair 
of  eyes  that  are  divided  in  such  a  way  that  it  is  thought 
that  one  part  looks  upward  into  the  air  (PI.  1085,  fig.  i, 
dorsal  view)  and  the  other  part  downward  into  the  water 
(fig.  2,  ventral  view). 

The  long,  flattened  larvae  of  the  Silphidae  or  burying 
beetles  (PI.  1086,  Necrophorus  tomentosus  Web.)  feed  upon 

1  Proc.-Ent.  Soc.  Washington,  II,  no.  3,  1892,  p.  344. 


METAZOA INSECTA .  435 

carrion  which  the  adults  (No.  1087,  Necrophorus  Carolina] 
have  provided. 

Accordi-ng  to  Kirby,1  a  pair  or  sometimes  more  than 
one  pair  of  these  insects  hunt  together.  When  a  dead 
bird  or  mouse  is  found,  the  pair  dig  the  earth  away  from 
under  it,  thus  sinking  it ;  the  female  then  allows  herself 
to  be  buried  with  the  carcass  until  after  her  eggs  are  laid, 
when  she  finds  her  way  to  the  surface.  The  sense  of 
smell  is  very  acute  in  these  beetles,  and  they  exhibit  much 
intelligence. 

The  rove  beetles  or  Staphylinidae  (No.  1088,  Staphy- 
linus  fossator)  have  become  specialized  by  reduction,  the 
wing  covers  or  elytra  being  short  though  still  performing 
the  same  function,  since  the  large  wings  can  be  folded 
and  packed  away  snugly  under  them. 

Still  more  reduced  are  certain  species  of  Adranes 
which  live  in  ants'  nests.  These  are  blind,  with  vestigial 
mouth  parts.  They  are  carefully  tended  by  the  ants,  and 
in  return  they  secrete  a  substance  which  collects  on  the 
tips  of  the  elytra  and  the  end  of  the  abdomen.2 

Among  the  beetles  some  of  whose  larvae  are  more  or 
less  like  the  Thysanura,  those  of  the  Lampyridae  are 
especially  interesting,  owing  to  a  peculiar  modification  in 
their  structure  whereby  light-giving  cells  are  produced. 
The  common  fire-fly,  Photuris  pennsylvanica  De  Geer, 
(No.  1089,  adult)  is  luminous  in  all  its  stages,  though 
most  brilliant  in  the  adult.  The  light-producing  cells  are 
in  the  abdomen,  and  they  are  surrounded  by  a  network 
of  tracheal  tubes.  The  cells  contain  yellowish  white 
granules  which  combine  with  the  oxygen  brought  by  the 
tracheae  and  thus  combustion  produces  light.  This 
chemical  process  does  not  depend  wholly  upon  the  life  of 
the  insect,  since  the  cells  when  taken  from  a  dead  beetle 
and  crushed  in  the  air  are  luminous  for  a  time. 3 

1  Text-Book  of  Ent.,  1885,  p.  29. 
2 Can.  Ent.,  XXXIII,  Jan.,  1901. 

3  See  Watase,  Woods  Hole  Marine  Biol.  Lab.,  Biol.  Lectures, 
1895. 


436  SYNOPTIC    COLLECTION. 

The  female  of  Lampyris  splendidula  has  neither  elytra 
nor  wings ;  these  females,  and  the  larvae  of  Lampyris 
generally,  are  luminous  and  are  called  "glow  worms," 
though  incorrectly,  since  they  are  not  worms  but  true 
insects. 

The  Scarabaeidae  represent  the  more  typical  Cole- 
optera,  many  of  whose  larvae  are  cylindrical  and  six- 
footed  grubs.  The  type  selected  is  the  common  June  or 
May  beetle,  Lachnosterna  fusca  Frohl.  Its  white  larva 
(No.  1090;  PI.  1091,  fig.  i)  lives  in  the  earth.  Its  head 
is  small  and  chitinous,  and  the  thoracic  and  abdominal 
segments  are  wrinkled.  This  wrinkled  appearance  is 
increased  by  the  habit  the  creature  has  of  coiling  and 
lying  partly  on  one  side  (fig.  i)  in  an  irregular  cavity 
which  it  has  formed.  It  also  moves  on  one  side,  and 
according  to  Lockwood1  the  larva  of  a  closely  allied  form, 
the  brilliant  goldsmith  beetle,  Cotalpa  lanigera  (No.  1093), 
travels  on  its  back  with  quite  a  rapid  serpentine  move- 
ment. 

The  grub  is  very  destructive,  eating  the  roots  of  grass, 
corn,  grain,  etc.  (PI.  1091,  fig.  2).  After  two  or  three 
years  the  larva  makes  a  well  defined  oval  cavity  and  lines 
it  with  a  secretion  from  its  own  body ;  it  then  changes 
to  a  pupa  (fig.  3)  in  which  the  parts  are  free.  Soon  after, 
the  pupa  becomes  a  beetle,  which,  according  to  Riley  is 
white  and  soft  at  first  but  remains  in  the  earth  until  hard- 
ened. Often  swarms  rise  from  the  earth  at  once,  and 
begin  immediately  to  eat  the  leaves  of  trees. 

The  short  body  of  the  beetle  (No.  1092  ;  PL  1091,  fig. 
4,  dissection -of  same)  like  that  of  the  other  typical  forms 
is  divided  into  the  three  regions.  The  head  is  small  and 
capable  of  being  withdrawn  under  the  prothorax  so  far  as 
the  eyes ;  when  extended,  the  short  neck  allows  the  head 
little  freedom  of  motion,  as  compared  with  carnivorous 
insects  like  the  dragon-fly.  The  prothorax  (fig.  4,  /)  is 

1  Amer.  Nat.,  II,  1869,  p.  190. 


METAZOA INSECTA.  437 

large  and,  excepting  the  small  mesothoracic  scutellum 
between  the  bases  of  the  wing  covers,  is  the  only  part  of 
the  thoracic  region  seen  from  above.  It  forms  with  the 
head  a  wedge-shaped  portion  of  the  body  of  advantage 
to  the  insect  when  digging  its  way  through  the  earth. 

When  the  elytra  and  wings  are  removed  the  small 
mesothorax  (fig.  4,  ms)  and  the  large  metathorax  (fig.  4, 
mt)  are  seen.  The  junction  of  the  thorax  and  abdomen 
is  broad  like  that  of  most  of  the  types  so  far  described. 

The  antennae  of  the  Scarabaeidae,  the  family  to  which 
the  May  beetle  belongs,  are  leaf-like  or  lamellate  at  the 
end  and  hence  the  name  Lamellicorns  often  given  to  the 
family.  The  antennae  are  usually  tucked  away  under 
the  eyes  and  are  extended  only  when  needed. 

The  mouth  parts  are  of  the  biting  type  and  are  similar 
to  those  of  the  Orthoptera.  The  six  legs  are  adapted 
pre-eminently  for  running.  The  wing  covers  or  elytra  are 
characteristic  organs  giving  the  name  of  Coleoptera,  mean- 
ing sheath  and  wing,  to  the  order.  These  elytra  are 
usually  considered  as  the  anterior  pair  of  wings  which 
have  become  horny,  but  in  which,  according  to  Dimmock,1 
the  remnants  of  veins  can  often  be  seen.  According  to 
Comstock,2  their  structure  "resembles  that  of  the  body 
wall  rather  than  that  of  wings,  and  in  some  beetles  (e.  g. 
Dytiscus)  rudiments  [remnants]  of  the  fore  wings  exist 
beneath  the  elytra."  The  wing  covers  are  of  little  use  in 
•flight  and  hence  the  small  size  of  the  mesothorax  which 
bears  them  ;  on  the  other  hand,  the  wings  are  useful  fly- 
ing organs  and  the  metathorax  is  consequently  large  and 
strong. 

There  is  no  external  ovipositor  and  the  abdomen  of  the 
male  and  female  are  alike,  excepting  that  in  the  former 
the  ventral  side  of  the  seventh  segment  has  a  transverse 
ridge.  Each  of  the  first  seven  abdominal  segments  has  a 

1  Stand.  Nat.  Hist.,  I,  1885. 

2  Manual  for  the  Study  of  Insects,  1895,  p.  494. 


438  SYNOPTIC    COLLECTION. 

pair  of  spiracles.1  The  May  beetle  like  all  beetles  is 
without  a  stinging  organ. 

Some  of  the  beetles  allied  to  the  Scarabaeidae  have 
greatly  developed  mandibles  like  those  of  Cladognathus 
(No.  1094). 

Among  the  large  beetles  of  the  United  States  is  Dynas- 
tes  (No.  1095,  larva;  No.  1096,  D.  tityrus  Linn.).  The 
thoracic  and  abdominal  regions  of  the  larva  are  immense 
as  compared  with  the  head.  The  legs  are  small  since  this 
stage  of  the  insect's  life  is  passed  in  rotten  wood. 

Coscinoptera  dominicana  Fabr.  is  an  interesting  form. 
It  fastens  its  eggs  on  long,  slender  stalks  (PI.  1097,  fig. 
i  ;  fig.  2,  egg,  magnified)  and  its  larva  (fig.  3)  makes  a 
case  for  itself  out  of  the  egg  shell  and  particles  of  earth 
(fig.  4)  which  it  carries  about.  Fig.  5  is  the  beetle 
enlarged. 

The  potato  beetle,  Doryphora  decemlineata  Say,  of  the 
family  Chrysomelidae,  is  another  good  type  of  the  Cole- 
optera,  but  it  is  much  smaller  than  Lachnosterna.  The 
larvae  (No.  1098)  are  short,  plump  grubs  that  are  ex- 
tremely active.  They  burrow  into  the  ground  where  the 
pupae  transform  to  the  adult  (No.  1099,  alcoholic  speci- 
men ;  No.  1 100,  dried). 

The  larvae  of  some  of  the  Chrysomelidae  when  young 
combine  characters  of  the  Thysanuriform  type  with  those 
of  Coleopterous  grubs,  while  the  full-grown  larvae  would 
be  called  caterpillars  by  those  not  knowing  that  this  term 
is  restricted  to  young  Lepidoptera.  The  three  pairs  of 
legs  in  the  young  larva  are  prominent  on  each  side  (PI. 
1 1 01,  fig.  2,  elm-leaf  beetle,  Galerucella  lute o la  Mull. ; 
fig.  i,  eggs  of  same),  while  the  body  is  rounded  and  grub- 
like.  The  feet  in  the  full-grown  larva  (fig.  3),  however, 
are  not  seen  from  above  but  only  in  a  side  view  and  the 
general  aspect  is  decidedly  that  of  a  caterpillar. 

When  full  grown,  the  larva  finds  a  sheltered  place  in 

'Willcox,  The  Observer,  July,  1896. 


METAZOA INSECTA.  439 

the  crevices  of  the  bark  or  on  the  ground  and  transforms 
to  a  pupa  (fig.  4)  which  in  a  shorter  or  longer  time,  ac- 
cording to  whether  the  month  is  July  or  October,  devel- 
ops into  the  beetle  (No.  1102;  PI.  1101,  fig.  5).  There 
may  be  two  and  possibly  three  broods  in  a  season  and  as 
both  larva  and  adult  feed  upon  the  elm  great  injury  is 
done. 

Still  more  striking  is  the  caterpillar-like  larva  of  Haltica 
chalybea  111.  (PL  1103,  fig.  i),  the  adult  (fig.  2)  of  which 
is  the  small  shining  blue  or  sometimes  greenish  beetle 
found  on  grape  vines  in  early  spring. 

The  caterpillar-like  larvae  of  beetles  may  be  hairy  in 
some  species  and  naked  in  others.  An  illustration  of  the 
former  is  found  in  the  carpet  beetle,  Anthrenus  scrophu- 
lariae  Fabr.  (No.  1104;  PL  1105,  fig.  i),  of  which,  al- 
though its  shape  is  unlike  that  of  a  caterpillar,  the  feet 
are  small  and  hidden  from  a  dorsal  view.  This  being  the 
case,  it  resembles  more  closely  a  hairy  caterpillar  than  a 
Thysanuriform  larva  or  a  typical  Coleopterous  grub.  It 
is  this  larva  which  does  most  of  the  damage  to  carpets 
and  woolen  goods.  The  larval  skin  serves  as  a  case  for 
the  pupa  (fig.  2,  dorsal  view  with  the  larval  skin  split 
down  the  back;  fig.  3,  the  pupa  removed  from  skin).  If 
the  pupa  transforms  normally,  its  skin  splits  lengthwise 
and  it  crawls  out  leaving  the  two  skins. 

The  wing  covers  of  the  beetle  are  provided  with  scales 
of  different  colors,  black,  brick- red,  and  white  (No.  1106). 
The  beetles  (No.  1106  ;  PL  1105,  fig.  4)  leave  our  houses 
and  feed  upon  the  blossoms  of  rhubarb ;  they  are  espe- 
cially fond  of  single  tulips,  particularly  the  yellow  shades.1 
Unfortunately  for  us,  the  beetles  return  to  our  houses  and 
lay  their  eggs  upon  the  food  which  their  young  love  best. 

The  larvae  of  some  species  of  the  family  Dermestidae 
have  a  brush  of  long  hairs  at  the  end  of  the  body  (PL 


1  I3th  Rep.  State  Ent.,  N.   Y.  State  Mus.,  1897,  p.  359.     This 
pamphlet  is  reprinted  from  the  5ist  Ann.  Rep.  N.  Y.  State  Mus.,  I. 


440  SYNOPTIC    COLLECTION. 

1107,  fig.  i,  Attagenus  piceus  OL).  In  this  species  the 
larva  is  a  reddish  brown,  while  the  pupa  (fig.  2)  is  white 
covered  with  a  delicate  pubescence.  The  adult  (No. 
1108;  PI.  1107,  fig.  3)  is  nearly  black  and  is  common  on 
window  sills  in  spring  and  early  summer. 

Many  of  the  Elateridae  or  spring-beetles  have  naked 
larvae,  as  seen  in  Alaus  oculatus  Linn.  (No.  1109,  larva, 
pupa,  and  adult).  The  adult  is  conspicuous  on  account 
of  the  scales  on  the  prothorax  which  are  arranged  in  two 
black  velvety  spots  encircled  by  white  rings.  The  beetles 
of  this  family,  when  they  have  fallen  on  their  backs,  can 
right  themselves  by  springing  into  the  air. 

Other  Elaterid  larvae  are  long,  cylindrical,  and  wire-like 
in  shape  with  a  smooth,  tough  cuticle,  such  as  the  larva 
of  Ludius  attenuatus  Say  (No.  1 1 10). 

Phosphorescence  is  not  limited  to  the  Lampyridae 
among  insects  but  is  found  in  members  of  other  families. 
The  most  beautiful  luminous  insect  we  have  seen  is  Pyro- 
phorus  nodiluca  Linn.  (No.  mi,  P.  physoderus)  of  the 
Elaterids.  When  flying  or  when  disturbed,  its  light  is 
given  out  from  two  spots  on  the  prothorax  and  one  on  the 
ventral  surface.  This  light  is  not  intermittent  as  in  the 
fire-fly,  but  is  steady,  strong  and  of  an  exquisite  greenish 
tint. 

The  larvae  of  some  of  the  Tenebrionidae,  Eleodes 
gigantea,  for  instance,  have  the  abdominal  segments  flat- 
tened at  first,  but  gradually  after  several  moults  of  the 
skin  they  acquire  the  typical  wire-like  shape  and  become 
darker  in  color.1  No.  1112  is  the  adult  of  Eleodes  trico- 
stata. 

Tenebrio  molitor  Linn.  (PL  1113,  fig.  i,  larva;  fig.  2, 
pupa;  fig.  3,  adult;  No.  1114,  adult)  is  a  well  known 
genus  of  this  family,  since  its  larva,  one  of  the  so  called 
"meal  worms,"  is  often  found  in  flour  and  meal. 

The  life  histories  of  the  parasitic  Coleoptera,  Meloidae 

1  Bull.  Brooklyn  Ent.  Soc.,  I,  no.  i,  1878,  p.  19. 


METAZOA INSECTA.  441 

and  Stylopidae,  are  instructive  inasmuch  as  they  throw 
light  on  the  life  history  of  the  group,  while  they  also  illus- 
trate the  changes  that  parasitic  habits  may  produce  on 
insect  structure. 

The  Meloidae  are  represented  by  Epicauta  vittata  Fabr. 
(PI.  1115;  No.  1116).  It  lays  its  eggs  (PI.  1115,  fig.  i) 
in  the  ground,  generally  near  the  egg-pods  of  locusts.  In 
about  ten  days  the  larva,  known  as  the  triungulin  (fig.  2), 
hatches.  It  is  soon  light  brown  in  color  and  very  active. 
Its  flattened  body  with  its  well  developed  legs  and  its 
cerci  give  it  a  Thysanuriform  aspect.  This  larva  bur- 
rows through  the  mucous  neck  of  a  locust's  egg-pod, 
Melanoplus  differentiates  (fig.  3,  egg- pod  of  M.  differ  en  ti- 
atis),  and  sucks  out  the  contents  of  an  egg.  In  time  the 
skin  splits  along  the  back  and  the  second  larva  (fig.  4) 
appears  with  the  legs  much  reduced  in  size.  Fig.  5  is  a 
side  view  of  this  same  larva,  showing  its  natural  position 
within  the  egg-pod.  The  last  stage  of  the  second  larva 
is  shown  in  fig.  6.  It  now  leaves  the  egg-pod  and  forms 
a  cavity  in  the  earth  in  which  it  lies  motionless,  and  is 
known  as  the  coarctate  larva,  called  by  fcabre  pseudopupa 
(fig.  7,  with  the  skin  adhering  behind  ;  fig.  8,  dorsal  view 
of  same).  The  legs  in  this  stage  are  little  more  than 
tubercles.  The  insect  usually  hibernates  in  this  condi- 
tion. In  spring  the  third  larva  appears,  which  is  very 
similar  to  the  coarctate  larva  excepting  that  it  is  active; 
but,  although  active,  it  seems  to  take  little  or  no  nourish- 
ment. In  a  few  days  this  larva  transforms  to  a  pupa  (fig. 
9,  pupa  of  Epicauta  cinerea  Forst.)  and  in  five  or  six  days 
the  imago  (No.  1116;  PI.  1115,  fig.  10)  is  fully  devel- 
oped. 

Thus  it  is  seen  that  the  Thysanuriform  larva  with  well 
developed  legs  becomes,  by  the  laws  of  variation  and 
adaptation  governing  animals,  a  creature  with  a  grub-like 
form  and  small  tuberculous  legs.  Specialization  by  re- 
duction, however,  is  not  carried  so  far  as*  to  produce  a 
footless  larva. 


442  SYNOPTIC    COLLECTION. 

The  young  of  Meloe  (No.  1117),  a  common  genus  in 
Massachusetts,  eat  the  eggs  of  the  bee  (Anthophora)  to 
which  they  are  borne  by  clinging  to  the  hairy  body  of  the 
mother.  The  second  larva  feeds  upon  the  honey  in  the 
cells  intended  for  the  larval  bee.  The  coarctate  stage 
gives  rise  to  an  active  fourth  (usually  called  the  third) 
larval  form  which  eats  its  way  out  of  the  cell  and  becomes 
a  pupa  from  which  the  dark  blue  beetle  emerges.  The 
latter  has  small  elytra  and  no  wings,  while  another  mem- 
ber of  this  family,  Hornia  minutipennis  Riley,  is  without 
wings  in  both  the  male  and  female  and  practically  with- 
out elytra  as  these  are  extremely  small. 

One  of  the  members  of  this  family,  Nemognatha  (No. 
1118),  is  of  especial  interest  since  its  mouth  parts  are 
similar  to  those  of  the  Lepidoptera.  The  two  maxillae 
are  long  and  hollowed  out  on  the  inner  side  so  that, 
when  pressed  together,  they  form  a  sucking  tube  for 
obtaining  the  sweet  juices  of  flowers. 

Specialization  by  reduction  is  carried  further  in  the 
Stylopidae  than  in  the  Meloidae,  since  the  larvae  which 
are  at  first  active  Hexapod  insects  finally  become  footless 
grubs,  while  the  adult  female  Stylops  is  little  more  than  a 
bag-like  creature  without  legs  or  wings.  PI.  1119,  fig. 
i,  represents  the  young  active  larva  of  Stylops  childreni 
Westw.  The  adult  male  Stylops  (fig.  2;  fig.  3,  side  view; 
PL  1 1 20,  enlarged  more  than  fig.  2  of  PI.  1119)  is  unique 
among  insects,  since  it  possesses  a  pair  of  club-shaped 
organs  on  the  mesothorax  which  resemble  the  metatho- 
racic  halteres  of  the  most  specialized  group  of  insects,  the 
Diptera.  The  wings  are  large  and  fan-shaped.  The 
female  Stylops  is  parasitic  in  the  abdomen  of  bees  (PI. 
1119,  fig.  4,  dotted  line  shows  its  body  in  natural  posi- 
tion ;  fig.  5,  taken  from  abdomen).  It  is  without  com- 
pound eyes,  legs,  or  wings,  and  is  viviparous. 

We  now  come  to  those  Coleoptera  which  have  skipped 
the  Thysanuriform  larval  stage  and  also  the  active  grub 
stage,  and  which  at  the  start  have  only  the  vestiges  of 
thoracic  feet  or  are  wholly  without  these  organs. 


METAZOA INSECTA.  443 

Most  of  the  Cerambycidae  are  tree-borers  in  the  larval 
stage  and  the  young  live  in  narrow  galleries  where  there 
is  little  need  of  feet.  These  organs,  therefore,  are  re- 
duced in  size  so  that  they  are  not  seen  from  above  (PI. 
1 12 1,  fig.  i,  Orthosoma  brunneum  De  Geer),  but  only  in 
a  ventral  view  (fig.  2,  probably  the  same  species). 

The  structure  of  these  small  thoracic  legs  is  better 
shown  in  PI.  1122,  fig.  2,  which  is  the  limb,  greatly 
enlarged,  of  the  oak  pruner,  Elaphidion  villosum  Fabr. 
(No.  1123;  PI.  1122,  fig.  5).  The  larva  (fig.  i)  burrows 
in  the  wood  under  the  bark  and  packs  the  burrow  with 
its  sawdust-like  castings.  It  selects,  as  a  rule,  a  small 
twig  consuming  the  wood  in  such  a  way  that  the  winds 
easily  sever  the  twig  so  that  it  falls  to  the  ground  with 
the  larva.  The  opening  at  the  severed  end  the  larva 
plugs  with  castings  and  in  this  closed  cell  transforms  to 
a  pupa  (fig.  3,  longitudinal  section  of  twig;  fig.  4,  cross 
section  of  same)  which  in  a  shorter  or  longer  time,  ac- 
cording to  temperature,  changes  to  a  beetle  that  cuts  its 
way  out  through  the  plug  of  castings. 

Some  of  the  Cerambycidae  have  footless  grubs  like  the 
Saperda  Candida  Fabr.,  or  the  round-headed  apple-tree 
borer  (PI.  1124,  fig.  i,  dorsal  view;  fig.  2,  side  view).  It 
feeds  when  in  the  larval  state  upon  the  sap-wood,  but  by 
the  end  of  the  second  year  it  reaches  the  solid  heart-wood. 
The  third  year  the  larva  gnaws  outward  to  the  bark  and 
makes  a  cell  for  itself.  Here  the  pupa  (fig.  3)  transforms 
to  the  adult  (No.  1125;  PI.  1124,  fig.  4)  which  cuts  its 
way  out  of  the  tree  by  its  sharp  mandibles. 

Chalcophora  virginica  Drury  (No.  1126),  of  the  family 
Buprestidae,  is  another  species  with  footless  larvae.  These 
live  in  the  pine  and  have  the  forward  part  of  the  body 
broad  and  flat.  The  adults  have  brilliant  metallic  hues 
(see  No.  1127,  ventral  side  of  same  species). 

The  Ambrosia  beetles  of  the  Scolytidae  are  interesting 
forms,  since,  according  to  Hubbard,1  they  exhibit  charac- 

1  U.  S.  Dep.  Agric.,  Bull.  Div.  Ent.,  n.  s.,  no.  7,  1897,  p.  9. 


444  SYNOPTIC    COLLECTION. 

teristics  in  the  care  they  take  of  their  young  that  are 
utterly  foreign  to  most  Coleoptera  and  such  as  we  shall 
find  farther  on  in  the  social  Hymenoptera. 

The  female  of  Platypus  compositus  deposits  her  eggs  in 
the  galleries  which  are  made  by  the  beetles  in  the  heart- 
wood  of  trees.  Here  young  (PI.  1128,  fig.  i)  and  old 
(fig.  2)  live  together,  and  the  galleries  are  always  kept 
clean  and  free  from  wood-dust.  The  larva  is  footless, 
but  its  ridges  and  tubercles  enable  it  to  move  rapidly 
through  the  galleries.  It  feeds  upon  Ambrosia,  a  kind  of 
fungus  (fig.  3)  which  is  carefully  propagated  by  the  beetles 
as  their  only  food  supply.  The  species  of  Ambrosia 
eaten  by  Platypus  has  erect  stems  with  swollen  cells  or 
conidia  at  their  ends.  Hubbard  says  that  "young  larvae 
nip  off  these  tender  tips  as  calves  crop  the  heads  of  clover 
but  the  older  larvae  and  the  adult  beetles  cut  the  whole 
structure  down  to  the  base  from  which  it  soon  springs  up 
afresh."  The  Ambrosia  is  started  by  the  mother  beetle 
upon  a  carefully  packed  bed  or  layer  of  chips.  In  some 
species  it  is  grown  only  in  certain  brood  chambers,  and 
in  others  "it  is  propagated  in  beds  near  the  cradles  of 
the  larvae."  The  excrement  of  the  larvae  is  used  to  form 
new  beds  for  the  propagation  of  the  fungus.  The  older 
larvae  assist  their  parents  in  excavating  the  galleries ;  in 
this  case  not  only  do  the  adult  beetles  care  for  their  young, 
but  the  larvae  "show  evident  regard  for  the  eggs  and 
very  tender  young  which  are  scattered  at  random  through 
the  passages,  and  might  easily  be  destroyed  by  them  in 
their  movements.  If  thrown  into  a  panic  the  young 
larvae  scurry  away  with  an  undulatory  movement  of  their 
bodies,  but  the  older  larvae  will  frequently  stop  at  the 
nearest  intersecting  passage  "  to  let  the  little  ones  pass, 
and  will  "  show  fight  to  cover  their  retreat."  * 

The  beetles  that  are  most  specialized  by  reduction  are 
the  Curculionidae  or  weevils.  The  tiny  strawberry  weevil, 

1  Loc.  tit.,  p.  15. 


METAZOA INSECTA.  445 

Anthonomiis  signatus  Say  (PI.  1129,  figs.  1-4,  greatly  en- 
larged), although  only  one  tenth  of  an  inch  in  length,  is 
an  extremely  clever  insect  and  exhibits  the  characters  of 
the  family. 

The  female,  with  her  long  snout,  parts  the  petals  of  a 
nearly  matured  bud  and  in  the  hole  thus  made  deposits 
her  egg.  The  sepals  and  petals  close,  never  to  open  into 
a  blossom.  The  beetle  then  crawls,  according  to  Chitten- 
den,  to  the  stem  below  the  bud  and  with  her  microscopic 
but  scissors-like  mandibles  cuts  it  in  such  a  way  that  the 
part  bearing  the  bud  hangs  by  a  mere  shred  and  soon 
falls  to  the  ground  (fig.  i,  showing  buds  ready  to  fall). 
The  development  of  the  bud  is  thus  arrested  long  enough 
for  the  larva  to  feed  on  the  pollen  and  the  food  is  kept 
moist  by  the  earth.  The  larva  (fig.  2,  full  grown)  is  foot- 
less and  fleshy  tubercles  have  taken  the  place  of  the 
jointed  legs.  After  devouring  the  pollen,  it  feeds  upon 
some  of  the  harder  parts  of  the  bud.  In  three  or  four 
weeks  it  utilizes  the  more  or  less  hollowed-out  bud  for  a 
cocoon,  transforming  to  a  pupa  (fig.  3)  and  finally  to  a 
beetle  (fig.  4).  The  latter  feeds  a  few  days  upon  the 
strawberry  blossoms  but  seldom  eats  the  leaves  and  never 
the  fruit.  It  would  seem  that  hibernation  begins  in  July, 
as  the  beetles  are  seldom  seen  after  the  middle  of  this 
month. 

The  structural  features  seen  in  the  strawberry  weevil 
are  peculiar  to  most  weevils.  The  larvae  are  footless 
though  sometimes  tubercles  or  bristles  are  developed. 
The  young  larva  of  Epicaerus  imbricatus  Say  (PI.  1130, 
fig.  i,  side  view  of  young  larva;  fig.  2,  adult,  both  en- 
larged), has  a  pair  of  stout  bristles  on  each  thoracic  seg- 
ment, and  these  aid  in  locomotion.  In  the  adult  the  head 
is  extended  into  a  longer  or  shorter  snout,  which  carries 
the  straight  or  elbowed  antennae.  The  mouth  parts  are 
usually  reduced  in  size  and  are  borne  at  the  end  of  the 
snout.  The  latter  organ  is  of  unusual  interest,  since  it 
has  acquired  the  function  of  an  ovipositor,  and  for  this 


446  SYNOPTIC    COLLECTION. 

reason  doubtless  has  grown  remarkably  long  in  some  spe- 
cies. 

The  elytra  are  more  chitinous  than  in  most  beetles, 
being  so  hard  that  it  is  difficult  to  thrust  an  insect 
pin  through  them.  They  are  sometimes  furnished  with 
scales,  as  in  the  diamond  weevil,  Entimus  imperialis, 
for  instance,  which  are  extremely  brilliant  microscopic 
objects. 

Clonus  scrophulariae,  like  some  other  weevils,  spins  a 
cocoon  from  a  secretion  of  its  body.  This  cocoon  is 
strikingly  like  the  seed  capsule  of  the  Scrophularia  nodosa, 
the  plant  upon  which  Cionus  feeds,  and  it  is  usually  fas- 
tened to  a  pedicel  of  the  seed  pod. 

The  chestnut  weevil,  Balaninus  proboscideus  Fabr. 
(formerly  B.  caryatryp.es  Bohm.),  (No.  1131)  is  excep- 
tional among  insects  owing  to  the  fact  that  its  mandibles 
are  vertical  instead  of  horizontal.  Its  proboscis  is  also 
longer  than  in  other  weevils,  often  being  in  the  female 
twice  the  length  of  the  body.  It  is  used  for  piercing  the 
burr  and  the  husk  of  the  chestnut  when  both  are  young. 
One  or  more  eggs  are  then  laid  in  the  nut  and  the  small 
puncture  soon  heals.  The  footless  larva  feeds  upon  the 
chestnut  until  ready  to  pupate,  when  it  leaves  the  nut  and 
enters  the  ground. 

Order  1 1.  —  NEUROPTERA. 

The  Neuroptera  includes  insects  which  have  Thysanu- 
riform  larval  characters,  although  combined  with  these 
characters  are  many  peculiar  modifications  of  structure 
that  ally  the  insects  with  the  more  specialized  order,  the 
Lepidoptera. 

The  larva  of  Corydalus  cornutus  Linn.  (No.  1132),  of 
the  family  Sialidae,  has  the  elongated  body,  the  distinct 
and  freely  movable  thoracic  and  abdominal  segments, 
and  the  three  pairs  of  well  developed  legs  of  the  Thysa- 


MET  AZO  A INS  ECT  A .  447 

nura.  It  also  has  the  biting  mouth  parts  of  the  general- 
ized insects.  But  in  addition  to  these  structural  features, 
Corydalus  has  nine  pairs  of  long  branching  filaments 
extending  from  the  sides  of  the  abdomen,  and  seven  pairs 
of  sponge-like  masses  also  used  for  respiration  (see  No. 
1132),  or  it  may  be  to  aid  the  animal  in  attaching  itself 
to  the  surface  of  stones  at  the  bottom  of  swift-flowing 
streams.1  Besides  these  branchial  organs  the  larva  is 
provided  with  the  tracheae  which  its  ancestors  possessed, 
and  which  are  useful  during  the  pupal  stage  that  lasts 
about  a  month  and  is  spent  in  a  cell  in  the  earth  under 
some  stone  or  log.  The  adult  (No.  1 133,  £  ;  No.  1 134,  9  ) 
is  a  giant  among  insects.  The  mandibles  of  the  female 
are  used  for  obtaining  and  masticating  food,  while  those 
of  the  male  are  weapons  and  also  clasping  organs.  The 
wings  expand  six  inches  (Packard)  but  as  the  thoracic 
segments  which  bear  them  are  unconsolidated,  we  should 
predict  that  the  flight  of  the  insect  would  be  slow,  and 
this  is  the  case. 

The  wings  have  an  open  network  of  veins.  The  name 
Neuroptera,  meaning  nerve  and  wing,  was  formerly  given 
to  an  order  of  insects  whose  typical  form  was  the  dragon- 
fly, and  the  significance  of  the  term  is  much  more  appar- 
ent when  we  consider  the  fine  network  of  veins  peculiar 
to  the  dragon-fly  wing  than  it  is  when  we  examine  the 
Corydalus  wing.  Now,  the  dragon-flies  are  placed  in  an 
order  by  themselves,  the  Odonata,  and  the  name  Neurop- 
tera is  retained  for  the  Sialidae,  Hemerobidae,  and  the 
like,  which  pass  through  an  indirect  development. 

One  of  the  interesting  Neuroptera  is  the  lace-winged 
fly  or  aphis-lion,  Chrysopa  perla.  The  female  has  the 
habit  of  fastening  her  eggs  at  the  tip  end  of  long  stalks. 
In  order  to  do  this  she  secretes  from  her  abdomen  a 
drop  of  a  tenacious  substance  which  she  draws  out  into  a 
thread ;  at  the  end  of  this  thread  she  places  a  knob  of 

1  Riley,  9th  Rep.  Benef.  and  Inj.  Insects  Mo.,  1877,  P-  I28- 


448  SYNOPTIC    COLLECTION. 

cement  to  which  she  attaches  an  egg  (No.  1135;  PI. 
1136,  fig.  i).  The  larva  (fig.  2)  crawls  out  and  is  Thy- 
sanuriform  in  general  aspect.  The  mouth  parts,  how- 
ever, are  specialized  for  sucking.  Each  mandible  is 
grooved  on  the  lower  side,  and  the  maxilla  fits  into  it  in 
such  a  way  that  a  tube  is  formed  through  which  the  blood 
of  the  prey  is  sucked.  The  eggs  are  laid  where  Aphides 
abound,  so  that  the  larvae  find  their  food  close  at  hand. 
When  ready  to  transform,  the  larva  spins  a  silken  cocoon 
(fig.  3).  The  adult  (No.  1137;  PI.  1136,  fig.  4)  cuts  a 
lid  in  this  cocoon  and  crawls  out.  It  has  brilliant  golden 
eyes,  biting  mouth  parts,  and  gauzy  wings  of  large  size 
compared  with  the  body  ;  but  the  flight  of  the  insect  is 
slow. 

Among  the  Coleoptera  we  have  found  the  larvae  of  the 
tiger  beetles  watching  for  their  prey  in  burrows ;  so  the 
larval  Myrmeleon  immaculatits  De  Geer,  or  ant-lion  of  the 
Neuroptera  digs  a  pitfall  (PL  1138,  fig.  i,  lower  portion, 
showing  insect;  fig.  i  a,  upper  portion  of  same)  in  dry 
loose  sand  and  buries  itself  at  the  bottom  with  the  excep- 
tion of  its  stout  mandibles  which  are  wide  apart  ready  to 
seize  whatever  insect  falls  in.  The  mouth  opening  of 
Myrmeleon  is  not  of  the  usual  character  but  is  com- 
pressed and  its  mandibles  are  like  those  of  Chrysopa,  so 
that  the  unfortunate  victim  that  has  fallen  down  the  pit  is 
held  by  the  mandibles  until  its  juices  are  sucked  out, 
when  the  empty  skin  is  thrown  some  distance  beyond  the 
pit  by  means  of  the  ant-lion's  head. 

The  mature  larva  makes  a  cocoon  by  fastening  grains 
of  sand  together  with  silk  spun  from  its  spinneret.  The 
adult  (No.  1139  ;  PI.  1138,  fig.  2)  has  biting  mouth  parts. 
Though  its  wings  are  large,  its  flight  is  weak  and  it  flies 
chiefly  at  night.  The  antennae  of  the  ant-lion  are 
slightly  swollen  at  the  ends,  but  this  tendency  is  carried 
so  far  in  Ascalaphus  (PI.  1140)  that  it  possesses  knobbed 
antennae  like  those  of  butterflies  of  the  order  Lepidoptera. 
In  short,  this  insect  strikingly  resembles  a  butterfly,  hav- 


METAZOA INSECTA.  449 

ing  besides  the  antennae  a  short,  thick  abdomen  and 
large,  gaily  colored  wings. 

A  good  example  of  differentiation  in  the  second  pair 
of  wings  is  found  in  Nemoptera  ledereri.  These  organs  are 
extremely  long  and  narrow,  swelling  out  at  their  ends  and 
appearing  like  paddles.  They  doubtless  aid  the  insect  in 
flying. 

As  the  development  of  Epicauta  threw  light  upon  the 
life  history  not  only  of  the  Coleoptera  but  also  of  the 
whole  class  of  Insecta,  so  the  development  of  Mantispa 
illumines  the  life  history  of  the  Neuroptera  and  strengthens 
our  hypothesis  in  regard  to  the  life  history  of  insects  in 
general. 

Mantispa  begins  its  life  as  a  Thysanuriform  larva  (PI. 
1141,  fig.  i,  M.  styriaca  enlarged).  This  larva  finds  an 
egg-case  of  a  spider  —  it  maybe  a  Lycosa  —  and  making 
a  small  opening,  crawls  into  the  sac.  There,  as  the  eggs 
hatch,  it  devours  the  young  spiders.  The  habitat  within 
the  spider's  egg-case  causes  marked  changes  in  structure. 
The  body  becomes  caterpillar-like  in  form  (fig.  2)  and 
the  head  small.  The  legs  are  reduced  in  size  and  in  the 
mature  larva  are  useless  vestiges,  while  the  antennae  are 
shortened.  The  larva  spins  a  cocoon  within  the  egg-sac 
and  the  pupa  develops  under  the  larval  skin.  The  adult 
No.  1142,  having  much  the  same  habit  as  the  praying 
mantis  (see  Nos.  1012,  1013),  has  a  similar  structure. 
The  prothorax  is  greatly  extended  and  the  fore  legs  are 
attached  at  the  forward  edge.  These  legs  are  long  and 
are  adapted  for  seizing  and  holding  prey,  being  held  in 
the  same  attitude  as- in  mantis. 


Order  12.  —  MECOPTERA. 

The  larvae  of  the  Mecoptera,  as  represented  by  the  type, 
Panorpa  communis  Linn.  (PL  1143,  fig-  I)>  are  caterpillar- 
like  in  general  aspect.  In  fact,  all  the  Mecoptera  larvae, 


450  SYNOPTIC    COLLECTION. 

so  far  known  to  us,  are  caterpillar-like  in  the  young  as 
well  as  in  the  mature  larval  stage,  though  some  species 
may  yet  be  found  that  passes  through  a  transient  Thysan- 
uriform  stage.  This  is  the  more  probable,  since  the 
Mecoptera  have  biting  mouth  parts  and  in  this  way  are 
more  generalized  than  the  Lepidoptera,  a  group  which 
we  shall  see  has  the  Thysanuriform  stage  represented  in 
the  life  history  of  one  of  its  generalized  members  (see  p. 
461). 

The  larva  of  Panorpa  (fig.  i)  is  not  only  provided  with 
thoracic  legs  ,but  it  has  also  eight  pairs  of  jointed  prop- 
legs  on  the  abdomen,  and  an  organ  called  the  anal  fork 
at  its  end  (see  fig.  i).  The  prop-legs  seem  to  be  of  little 
use,1  but  locomotion  is  accomplished  by  the  thoracic  legs 
and  anal  fork,  the  latter  being  capable  of  supporting  the 
body.  Besides  the  prop-legs,  the  young  larva  has  spines 
which  disappear  in  the  mature  larva,  excepting  those  on 
the  eighth,  ninth,  and  tenth  segments.  Like  caterpillars, 
Panorpa  has  a  pair  of  spiracles  in  the  prothorax,  but  none 
in  the  mesothorax  or  metathorax,  while  there  is  a  pair  in 
each  of  the  first  eight  abdominal  segments. 

The  larva  burrows  in  the  ground  and  there  becomes  a 
pupa.  The  head  of  the  adult  (No.  1144,  <£,  9  ;  PL  1143, 
fig.  2)  is  extended  into  a  beak,  at  the  end  of  which  are  the 
mouth  parts.  According  to  Felt,2  feeding  is  a  combina- 
tion of  biting  and  sucking,  and  only  wounded  or  dead 
animals  were  eaten  by  the  species  under  observation. 

The  long  abdomen  of  the  male  is  provided  with  a  pair 
of  forceps-like  claspers  and  is  bent  over  the  back,  giving 
the  insect  somewhat  the  appearance  of  a  scorpion, 
although  the  two  animals  are  very  different. 

Another  member  of  the  Mecoptera  is  Bittacus  tipularius 
which  is  a  slender  insect  with  remarkably  long  legs,  but 
without  the  forceps-like  abdominal  appendages  of  Panorpa. 

• 

1  Felt,  loth  Rep.  N.  Y.  State  Ent.,  1895. 

2  Loc.  tit.,  p.  466. 


METAZOA INSECTA.  451 

The  legs  are,  in  fact,  so  long  that  the  insect  never  stands 
upon  them,  and  therefore  never  alights  but  suspends  it- 
self from  a  twig  by  its  long  fore  legs,  sometimes  using  also 
its  second  pair.  In  this  situation  it  has  cleverly  adapted 
its  hind  legs  for  seizing,  using  them  as  hands  (Brauer). 
The  mouth  parts  are  better  fitted  for  piercing  than  those 
of  Panorpa,  and  living  insects,  preferably  flies,  are  the 
diet. 

The  wingless  condition  is  represented  in  the  Mecop- 
tera  by  the  female  Boreus  hiemalis  (PI.  1145),  which  is 
sometimes  found  on  snow.  The  head  is  extended  into  a 
beak,  as  in  the  other  Mecoptera,  and  the  female  has  an 
external  ovipositor  while  the  hind  legs  are  adapted  for 
leaping. 

Order  13. —  TRICHOPTERA. 

The  Phryganidae  or  caddis-flies  are  the  only  members 
of  the  Trichoptera.  The  larvae  are  caterpillar-like  from 
the  start,  although  their  aquatic  life  (together  with  the 
habit  of  carrying  a  protective  case  about  with  them)  has 
caused  such  modifications  in  structure  that  they  are  not 
so  strikingly  like  caterpillars  as  the  larvae  of  Mecoptera. 
They  are,  however,  nearer  the  caterpillar  than  the  Thysa- 
nuriform  type. 

The  adults  do  not  closely  resemble  the  imagoes  of  any 
of  the  orders  so  far  described,  but  their  resemblance  to 
moths  of  the  order  Lepidoptera  is  most  marked. 

Anabolia  is  a  common  genus  in  New  England.  The 
forward  part  of  the  body  of  the  larva  (No.  1146;  PL 
1147,  fig.  i)  is  chitinous  owing  to  exposure,  while  the 
posterior  part,  being  covered  with  a  case,  is  soft  and  light 
colored.  The  case  (No.  1146;  PI.  1147,  fig.  2)  in  tn^s 
genus  is  made  of  sticks  and  stones,  and  is  fastened  to  the 
body  by  means  of  two  hooks  at  the  end  of  the  abdomen, 
while  it  is  probable  that  the  three  tubercles  on  the  first 
abdominal  segment  also  aid  in  this  work.  As  the  larva 


452  SYNOPTIC    COLLECTION. 

drags  its  case  about  with  it  by  means  of  its  legs  and  some- 
times its  mandibles,  these  parts  are  well  developed.  The 
case  is  large  enough  for  the  respiratory  filaments  on  each 
side  of  the  abdomen  (fig.  i)  to  move  freely  in  the  water. 
In  fact,  the  larva  is  able  to  turn  itself  in  its  case  so  that 
its  head  appears  indiscriminately  at  either  end.1  The 
larva  is  exceptional  in  having  no  antennae  and  at  the 
same  time  small  eyes,  for  when  the  former  organs  are 
absent  the  eyes  are  usually  well  developed. 

When  the  larva  is  ready  to  become  a  pupa  (fig.  3),  it 
closes  both  ends  of  its  tube  with  silk  spun  from  the  spin- 
neret which  is  near  the  mouth,  as  in  Lepidopterous  cater- 
pillars. During  the  pupal  stage  the  antennae  develop, 
the  mouth  parts  become  reduced  in  size,  though  the 
mandibles  still  persist,  and  the  respiratory  filaments  disap- 
pear. 

The  appendages  of  the  pupa  are  free  as  in  all  the 
pupae  so  far  described. 

The  adult  (PL  1147,  fig.  4)  has  a  small  head,  a  collar- 
like  prothorax,  a  comparatively  large  mesothorax,  and  a 
slender  abdomen  —  characters  which  we  shall  see  are 
shared  by  moths.  The  caddis-fly  (No.  1148,  Neuronia, 
one  of  our  largest  species)  also  possesses  hairy  wings 
(hence  the  name  Trichoptera,  meaning  hair  and  wing), 
which  sometimes  become  scale-like.  The  two  wings  on 
each  side  are  fastened  together  so  that  they  act  as  one 
thereby  increasing  the  power  of  flight.  When  at  rest  the 
wings  are  held  roof-like  over  the  body. 

The  mouth  parts  of  the  adult  are  transitional  between 
the  biting  and  sucking  type.  The  mandibles  are  obsolete, 
and  in  some  genera,  according  to  Hagen,2  the  mouth 

1  McLachlan,  Trans.  Ent.  Soc.  London,  (3),  V,  1865,  p.  n. 

2  Quoted  by  Packard,  Ent.  for  Beginners,  1889,  p.  90. 


METAZOA INSECTA.  453 

organs  form  a  proboscis  which  is  adapted  for  probing 
flowers  and  obtaining  the  sweet  nectar. 

The  cases  of  caddis-flies  are  exceedingly  varied  and 
ingenious  little  objects.  Leptocerus  (PI.  1149,  fig.  i) 
builds  a  straight  tube  of  sand.  Limnephilus  vittatus 
Fabr.  has  a  slightly  curved  tube  of  the  same  substance 
(fig.  2),  while  Helicopsyche  makes  the  young  or  nepionic 
part  of  its  case  straight,  while  the  older  or  ephebic  portion 
(fig.  3  ;  PL  1150,  fig.  2)  is  coiled  like  a  snail  shell.  Fritz 
Miiller  x  says,  that  "  when  preserved  in  adult  specimens 
the  oldest  portion  [in  reality  the  young  shell]  peeps  out 
from  the  top  of  the  heliciform  case  like  a  little  chimney." 

The  body  of  the  caddis-fly  is  not  spiral  like  that  of  the 
snail  but  symmetrical  like  that  of  other  Trichopterous 
larvae,  as  shown  in  PI.  1150,  fig.  i.  When  ready  to 
transform,  the  larva  (fig.  2,  in  its  case)  spins  an  oper- 
culum  (fig.  3)  which  has  concentric  lines  like  many  of 
the  opercula  of  Gastropods,  but  unlike  the  latter  this  oper- 
culum  has  a  slit  for  the  admission  of  water. 

Some  caddis-flies,  like  Setodes  tineiformis,  do  not  select 
foreign  substances  for  their  cases,  but  spin  them  entirely 
of  a  secretion  from  their  own  bodies,  popularly  known  as 
"  silk." 

The  caddis-fly  larvae  already  described  are  free-moving 
and  live  in  comparatively  still  water,  but  there  are  others 
living  in  swift  flowing  streams  that  attach  their  habitations 
to  stones  and  the  like.  One  of  the  most  ingenious  of  this 
group  is  Hydropsyche  (PI.  1151).  It  builds  its  case  of 
sand  or  of  bits  of  plants,  fastening  it  to  a  stone  so  that 
the  latter  forms  the  lower  part  of  the  case  (PI.  1152). 
Close  to  the  opening  of  the  case  it  erects  a  vertical  frame- 
work across  which  it  stretches  a  net.  The  food  brought 
down  by  the  current  is  caught  by  the  net  and  the  larva 
can  eat  its  meal  without  wholly  leaving  its  house  (see 
PL  1152). 

'Trans.  Ent.  Soc.  London,  1879,  p.  132. 


454  SYNOPTIC    COLLECTION. 

In  the  family  of  Limnophilidae,  the  members  of  which 
have  slightly  curved  horn-like  cases,  as  seen  in  PI.  1153, 
fig.  2,  there  is  one  genus,  Enoicyla  pus  ilia  Burm.  (PL 
1153,  figs.  1-3),  that  lives  on  the  land.  This  is  the  only 
Trichopterous  insect  so  far  known  that  is  terrestrial. 
The  figure  of  the  larva  (fig.  i  ;  fig.  2,  larva  in  its  case) 
does  not  exhibit  any  vestiges  of  respiratory  filaments 
which  we  should  expect  to  find  if  the  ancestors  were 
aquatic.  It  may  be,  however,  that  a  sufficient  period 
of  time  has  elapsed  for  the  terrestrial  habitat  to  cause  the 
complete  disappearance  of  the  branchial  filaments.  This 
seems  the  more  probable  since  the  female  (fig.  3)  is  spe- 
cialized by  reduction,  having  lost  both  pairs  of  wings.  If 
this  is  not  the  case,  then  the  insect  is  primary  and  should 
be  placed  as  the  most  primitive  of  the  Trichoptera. 

Order  14.  —  LEPIDOPTERA. 

The  caterpillar-type  of  larva  has  now  become  so  fixed 
in  the  insect  organization  that  it  is  found  with  scarcely 
an  exception  in  the  members  of  this  immense  order  of 
Lepidoptera.  The  variations  that  occur  are  mainly  in  the 
minor  details  of  structure,  while  the  fundamental  form  and 
characters  remain  essentially  the  same.  Although  this 
is  true  speaking  broadly,  we  shall  see  farther  on  that  there 
is  one  moth,  Melittia  satyriniformis  Hbn  ,  which  throws 
light  on  the  genealogy  of  the  order,  since  it  passes 
through  a  stage  when  first  hatched  that  is  comparable 
with  the  Thysanuriform  stage  of  the  more  generalized 
insects.  This  stage,  however,  is  brief,  and  the  larva  has 
attained  the  caterpillar  form  when  half  grown.-  As  we 
have  stated  elsewhere  the  common  custom  of  calling  cat- 
erpillars "worms"  is  misleading  and  therefore  has  not 
been  followed  in  this  work.  The  word  was  given  because 
the  caterpillar,  like  the  worm,  is  cylindrical  and  seg- 
mented, but  if  all  cylindrical,  segmented  animals  were  to 


METAZOA INSECTA.  455 

be  called  worms,  our  classification  would  be  most  errone- 
ous. When  it  is  borne  in  mind  that  the  caterpillar  is  a 
specialized  animal,  as  compared  with  the  worm,  having 
well  developed  mouth  parts,  jointed  legs,  adaptive  prop- 
legs,  and  embryo  wings,  it  becomes  evident  that  the  reten- 
tion of  "worm  "  as  descriptive  of  young  Lepidoptera  leads 
only  to  a  confusion  of  ideas  which  is  always  to  be 
avoided. 

The  moths  constitute  the  more  primitive  group  cf  the 
Lepidoptera  or  scaly-winged  insects,  while  the  butterflies 
are  more  specialized.  This  arrangement,  based  on  struc- 
ture and  development,  is  in  harmony  with  the  palaeonto- 
logical  record  of  the  order. 

Jugatae.  Eriocephala  calthdla  possesses  characters 
allying  it  with  the  Neuroptera,  Mecoptera,  and  Trichop- 
tera.  The  caterpillar  (PI.  1154,)  is  provided  with  eight 
pairs  of  abdominal  prop-legs,  each  ending  in  a  curved 
spine  and  resembling  the  similar  prop-legs  of  the  Panorpa 
larva.  It  is  specialized  by  addition  in  possessing  rows 
of  odd  ball-like  appendages.  The  adult  has  the  collar- 
like  prothorax,  while  the  mesothorax  and  metathorax  are 
long  and  slightly  consolidated.  These  two  thoracic  seg- 
ments are  of  nearly  equal  size,  like  the  two  pairs  of  wings 
which  they  bear.  These  wings  are  similar  in  their  vena- 
tion and  are  fastened  together  by  a  membranous  lobe,  the 
jugum  (see  PI.  1157,  fig.  i,/),  extending  from  the  pos- 
terior basal  part  of  the  fore  wing  ;  in  this  way  these  moths 
resemble  the  Trichoptera. 

The  wings  are  covered  with  scales  or  modified  hairs, 
the  common  character  of  the  order,  and  in  addition  to 
these  scales  there  is  a  covering  of  fine  hairs,  which, 
according  to  Kellogg1  are  found  in  the  Jugatae  but  not 
in  the  more  specialized  Frenatae.  A  similar  coating  of 
hairs  is  found  in  the  Trichoptera,  which  indicates  that  it 


1  Kansas    Univ.  Quarterly,  III,  no.  I,  1894,  p.  80;  also  Amer. 
Nat.,  XXIX,  1895,  p.  250. 


456  SYNOPTIC    COLLECTION. 

is  a  generalized  feature  and  was  probably  possessed  by 
the  stem  form  of  the  Lepidoptera. 

The  mouth  parts  of  Eriocephala  are  unique  among 
Lepidoptera.  The  first  pair  of  maxillae  have  an  inner 
lobe,  the  galea  (PI.  1155,  fig.  2,  £•)  and  an  outer  lobe, 
lacinia  (fig.  2,  /),  besides  the  palpi  (fig.  2,  mxp} .  These 
lobes  are  homologous  with  the  same  parts  in  the  mandibu- 
late  insects.  Eriocephala  is  the  only  Lepidopteran  known 
that  possesses  the  lacinia,  as  it  is  usually  the  two  galeae 
which  unite  to  form  the  sucking  tube.1  According  to 
Chapman2  these  moths  use  the  great  claw-like  maxillary 
palpi  with  sharp  knife-points  to  scrape  and  tear  at  both 
the  pollen  of  the  stamens  and  the  surface  of  the  petals, 
in  the  latter  case  perhaps  collecting  fallen  pollen. 

The  second  pair  of  maxillae  are  also  provided  with  two 
lobes  and  a  palpus.  Besides  the  maxillae  there  is  a  pair 
of  toothed  mandibles  (fig.  i)  which  are  used  as  in  the 
biting  insects. 

Hepialus  argenteomaculatus  is  another  moth  belonging 
to  the  Jugatae.  The  caterpillar  is  naked  and  has  the 
three  pairs  of  thoracic  legs  and  five  pairs  of  prop-legs. 
It  pupates  in  the  earth  like  many  beetles.  The  hind 
wings  of  the  adult  (No.  1156)  are  much  longer  than  in 
most  Lepidoptera,  but  the  venation  of  the  wings  is  simple 
(see  PI.  1157,  figs.  A,  B,  H.  gracilis).  As  in  Eriocephala 
the  fore  and  hind  wings  are  fastened  by  the  jugum  (fig. 

A,/). 

The  remaining  moths  and  butterflies  belong  to  the 
Frenatae,  since  instead  of  a  jugum  for  fastening  the  wings 
together,  many  Frenatae  have  a  frenulum  which  is  a 
strong  spine  in  the  male  and  a  bunch  of  bristles  in  the 
female  borne  on  the  front  edge  of  the  base  of  the  hind 
wing  (PI.  1158,  fig.  B,y").  In  the  male  the  frenulum  fits 
into  a  hook  on  the  lower  surface  of  the  fore  wing  (fig.  A) 
but  the  female  seldom  has  this  hook. 


1  Packard,  Amer.  Nat.,  XXIX,  1895,  P-  637- 

2  Trans.  Ent.  Soc.  London,  1894,  p.  338. 


METAZOA INSECTA.  457 

According  to  Comstock,  whose  natural  classification  of 
the  Lepidoptera  we  have  adopted  essentially,  the  Frenatae 
which  do  not  now  possess  a  frenulum  (some  moths,  all 
skippers,  and  butterflies)  have  gradually  lost  it,  owing 
probably  to  the  large  development  of  the  front  edge  of 
the  basal  portion  of  the  hind  wing  which  fits  under  the 
fore  wings  so  closely  that  unity  of  action  is  made  possible. 
The  frenulum,  not  needed,  would  gradually  tend  to  disap- 
pear.1 

Frenatae.  The  larvae  of  the  flannel  moths  of  the 
family  Megalopygidae  have  seven  pairs  of  prop-legs 
besides  the  three  pairs  of  thoracic  legs  (No.  1159,  upper 
left  hand  specimen  of  Megalopyge  crispata}.  They  make 
a  trap-door  cocoon  (No.  1159,  lower  left  hand  specimen). 
The  adult  (No.  1159,  right  hand  specimen)  is  covered 
with  crinkly  hair  and  hence  the  popular  name. 

The  Psychidae  remind  one  of  caddis-flies,  since  their 
caterpillars  make  a  bag  and  cover  it  with  sticks  (No.  1160, 
Psyche  pulld)  which  they  carry  about  with  them.  The 
adult  (No.  1161,  $)  is  one  of  the  small  moths.  The 
wingless  female  is  specialized  by  reduction  and  is  an  illus- 
tration of  suppressed  development.  This  reduction  is 
clearly  shown  in  the  evergreen  bag-worm,  Thyridopteryx 
ephemeraeformis  Haw.  (PI.  1162,  figs.  1-6).  If  the  larva 
(fig.  T;  fig.  2,  in  case  or  "bag")  is  to  become  a  male 
(according  to  Riley  the  caterpillars  are  all  alike  until  the 
pupal  stage  is  reached,  when  the  sexes  are  differentiated), 
the  development  proceeds  as  in  most  Lepidopterous  in- 

iDr.  A.  S.  Packard  (Mem.  Nat.  Acad.  Sci.,  VII,  Monograph  i, 
^95,  p-  57)  objects  to  this  division  of  the  Lepidoptera  into  the 
Jugatae  and  Frenatae  on  the  ground  that  the  characters  are  too 
slight,  considering  that  the  structure  of  the  mouth  parts  and  more 
especially  the  characters  of  the  pupa  are  of  fundamental  importance 
in  working  out  the  phylogeny  of  the  group. 

For  our  .present  purpose,  however,  the  classification  given  by 
Comstock  is  more  simple  and  more  in  harmony  with  that  of  the 
other  orders  of  insects,  while  at  the  same  time  it  is  based  on  philo- 
sophical reasoning. 


458  SYNOPTIC    COLLECTION. 

sects  and  the  pupa  (fig.  3)  becomes  a  winged  male  (fig. 
4)  ;  but  if  the  larva  is  to  be  a  female,  it  remains  in  the 
pupa-case  (fig.  5,  female  with  split  pupa  skin)  and  becomes 
little  more  than  an  egg-sac  (fig.  6).  Its  legs  and  antennae 
are  lost  and  the  wings  never  develop ;  in  fact,  it  has  no 
external  features  that  would  place  it  in  the  order  Lepidop- 
tera.1  When  egg  laying  is  accomplished,  little  is  left  of 
the  body  of  the  parent.  The  "  weather-beaten  bags,"  full 
of  yellow  eggs,  are  tightly  fastened  to  the  twigs  of  trees 
and  in  this  secure  situation  usually  pass  the  winter  suc- 
cessfully. 

Other  maths  belonging  to  the  generalized  Frenatae  and 
affording  illustrations  of  specialization  by  reduction  are 
the  Cossidae  or  carpenter  moths,  the  larvae  of  which  are 
borers.  Like  the  young  of  the  Cerambycidae  or  boring 
beetles  these  larvae  are  more  or  less  grub-like  in  form, 
and,  although  thoracic  legs  and  prop-legs  are  present,  they 
are  reduced  in  size  and  are  not  seen  in  a  dorsal  view  (PL 
1 163,  fig.  i,  young  caterpillar  of  Cossus  centerensis  Lintner, 
or  the  poplar  goat  moth  ;  fig.  2,  mature  caterpillar,  three 
years  of  age).  The  larvae  excavate  burrows  in  wood  by 
means  of  their  strong  black  mandibles,  and  one  has  been 
known  to  bore  through  a  large  leaden  bullet  which  was 
embedded  in  an  oak  tree. 2 

At  the  end  of  three  years  a  pupa  cell  or  cocoon  (fig.  3) 
is  formed  which  is  apparently  an  enlarged  and  more  care- 
fully finished  burrow.  Filling  the  exit  end  are  coarse 
and  fine  wood-scrapings  through  which  the  pupa  (fig.  4, 
9  )  passes  to  the  exterior  where  it  becomes  the  winged 
insect  (fig.  5,  9  ,  showing  ovipositor). 

The  reduced  condition  of  the  legs  is  carried  still  further 
in  the  Eucleidae  or  slug  caterpillar  moths.  In  these  lar- 
vae neither  legs  nor  prop-legs  can  be  seen  in  a  side  view 
and  the  larva  appears  to  be  legless.  The  prop-legs,  in 

1  Lintner,  ist  Ann.  Rep.  Ins.  N   Y.,  1882,  p.  82. 

2  U.  S.  Dep.  Agric.,  Div.  Ent.,  Bull.  10  (n.  s.),  1898,  p.  88. 


METAZOA INSECTA.  459 

fact,  should  hardly  be  called  by  the  name,  since  they  are 
mere  swellings. 

The  more  specialized  Frenatae  may  be  divided  into  two 
groups :  one  represented  by  the  Orneodidae,  Pyralidae, 
Tortricidae,  Tineidae,  and  Sesiidae,  and  the  other  by  the 
so  called  frenulum  conservors  and  the  frenulum  losers. 

The  larvae  of  the  plume  moths  or  Orneodidae  spin  no 
cocoon  but  they  often  fasten  themselves  within  a  curved 
leaf,  thereby  showing  a  tendency  towards  cocoon  making. 
The  adults  (No.  1164,  Orneodes  hexadactyla  Linn.)  of 
some  species  have  each  of  the  four  wings  divided  into 
six  parts,  giving  a  feathery  appearance  to  these  organs  of 
flight. 

The  Pyralidae  are  especially  interesting  since  certain 
larvae  of  this  family  have  become  adapted  for  aquatic  life. 
Tufts  of  respiratory  filaments  or  gills  which  are  supplied 
with  special  air-tubes  occur  on  each  side  of  the  body  (PI. 
1165,  fig.  i,  Paraponyx  obscuralis  Gr. ;  fig.  2,  respiratory 
filament).  The  air  contained  in  the  water  passes  through 
the  walls  of  the  filament  and  supplies  the  tubes.  These 
caterpillars,  according  to  Hart,1  are  usually  concealed  by 
leaves  which  the  insect  has  fastened  together  with  silk ; 
when  these  hiding  places  are  broken  up,  the  caterpillars 
swim  about  in  the  water.  The  larva  spins  a  dense  cocoon. 
The  pupa  (fig.  3)  is  without  gills,  but  has  conspicuous 
spiracles  on  either  side.  According  to  Miall*  the  cocoon 
of  Paraponyx  stratiotata  though  immersed  in  water,  is 
filled  with  air,  and  the  facts  tend  to  prove  that  the  spir- 
acles of  the  pupa  are  used  in  respiration. 

The  larvae  of  the  Tortricidae  have  the  habit  of  rolling 
up  leaves  which  serve  both  for  a  habitation  and  for  food. 
Here  they  live  together  in  companies.  When  ready  to 
transform  the  pupae  cling  to  the  surface  of  the  nest,  while 
the  winged  insects  fly  away  leaving  the  empty  pupa  skins 
as  seen  in  No.  1166. 


1  Bull.  111.  State  Lab.  Nat.  Hist.,  IV,  1895,  p.  167. 

2  Nat.  Hist.  Aquatic  Insects,  1895,  p.  233. 


460  SYNOPTIC    COLLECTION. 

The  young  Tortrix  testudimana  has  no  prop-legs,  while 
the  six  thoracic  legs  are  so  small  that  they  are  difficult  to 
perceive  and  are  of  little  use.  No.  1167  is  an  adult 
Tortricid,  Cacoecia  rosaceana. 

One  of  the  best  known  families  of  moths  is  the  Tinei- 
dae,  represented  by  the  familiar  clothes  moth,  Tinea  pellio- 
nella  Linn.,  and  by  Coptodisca  (  =  Aspidisca)  splendor  if er- 
ella  Clem. 

Tinea  pellionella  Linn.,  produces  at  the  north  but  one 
generation  in  a  year.  Under  normal  conditions  the  eggs 
are  laid  from  May  to  August,  but  in  furnace-heated  houses 
the  moths  are  often  seen  in  April,  and  sometimes  as 
early  as  March,  so  that  the  eggs  in  these  cases  are  laid 
earlier.  In  about  a  week  the  eggs  hatch  and  the  larvae 
(PI.  1168,  fig.  i)  begin  to  feed  at  once.  They  can  live, 
if  necessary,  upon  almost  any  dry  animal  matter,  but 
since  the  earliest  times  they  have  preferred  to  infest  our 
houses  and  feed  upon  woolen  goods,  fur,  feathers,  and 
even  cotton  cloth.  The  larvae  do  all  the  damage.  As 
soon  as  hatched,  the  larva  makes  a  protective  case  for 
itself  from  the  material  on  which  it  feeds.  This  case 
(fig.  2)  it  seldom  leaves  but  as  the  animal  grows  larger 
it  increases  the  size  of  its  protective  covering  by  slitting 
the  edge  and  setting  in  gores.  By  turning  about  in  its 
case  it  is  able  to  do  this  at  each  end. 

The  larva  reaches  its  full  size  toward  winter;  it  then 
finds  a  safe  place  where  it  fastens  itself  securely  and  in 
its  closed  case  remains  torpid  till  spring.  The  moth 
(No.  1169;  PI.  1168,  fig.  3)  is  dull-colored  and  expands 
about  one  half  inch.  Its  mouth  parts  are  in  such  a  ves- 
tigial condition  it  cannot  obtain  food  and  after  egg-laying 
is  completed  it  dies. 

Coptodisca  (  =  Aspidisca]  splendoriferella  Clem.,  when  a 
larva  (PI.  1170,  fig.  i),  lives  in  apple  tree  leaves,  mining 
the  parenchyma  between  the  two  layers  (fig.  2).  In  the 
autumn  it  makes  a  case  for  itself  from  the  layers  of  the 
leaf  and  travels  about  (fig.  3),  selecting  a  spot  on  the 


METAZOA INSECTA.  461 

trunk  or  branches  where  it  can  spend  the  winter.  Several 
of  these  attached  hibernating  larvae  are  seen  on  the 
branch  in  fig.  2,  and  the  larva  with  the  case  removed  in 
fig.  4.  In  the  spring  the  larva  changes  to  a  pupa  (fig.  5) 
and  finally  becomes  the  winged  adult  (fig.  6). 

The  habit  of  leaf  mining  in  the  larval  state  has  brought 
about  a  reduction  of  the  locomotor  organs  of  Coptodisca, 
so  that,  according  to  Clemens,1  there  are  no  thoracic  legs 
but  rather  cup-like  depressions  on  both  the  ventral  and 
dorsal  side  which  are  capable  of  contraction  and  expan- 
sion. Neither  are  there  prop-legs,  but  in  their  places  are 
folds  of  the  integument  which  act  as  substitutes  for  these 
organs. 

This  tendency  towards  reduction  and  loss  of  the  legs  is 
carried  so  far  that  in  Phyllocnistis,  according  to  the  same 
author,2  not  only  are  there  no  legs  nor  prop-legs,  but  vol- 
untary motion  has  almost  wholly  ceased. 

The  Sesiidae  or  clear-winged  moths  are  represented 
by  Melittia  satyriniformis  Hbn.  (PI.  1171,  figs.  1-7). 
This  genus  is  especially  interesting  since  the  newly 
hatched  larva  (fig.  i)  is  similar  to  the  Thysanuriform 
stage  of  the  more  primitive  insects.  The  shape  of  its 
body,  the  three  pairs  of  legs  which,  though  small,  are 
plainly  seen  from  above  extending  outward  on  either  side 
of  the  thorax,  the  bristles  at  the  posterior  end  of  the  body, 
are  all  characters  suggestive  of  the  Thysanura  and  the 
Thysanuriform  stage  of  development.  This  stage,  how- 
ever, is  quickly  passed  over,  so  that  the  half-grown  larva 
(fig.  2)  has  the  caterpillar  form.  The  mature  larva  (fig. 
3)  is  a  borer  in  the  hollow  stems  of  the  squash  vine,  and 
it  shows  adaptation  to  its  habitat  by  the  reduced  condition 
of  the  legs. 

Like  many  beetles,  Melittia  descends  into  the  earth  to 

^.S.  Dep.  Agric.,  Rep.  of  Entomologist,  by  Comstock,  1879, 
p.  213. 

2  Tineina  of  N.  A.,  1872,  p.  25. 


462  SYNOPTIC    COLLECTION. 

pupate.  There  it  spins  a  silken  cocoon  (fig.  4)  that  is 
black  inside  and  out,  and  changes  to  a  pupa  (fig.  5). 
The  latter  is  provided  with  a  horn-like  process  on  its  head 
(see  fig.  5)  for  opening  a  way  out  of  the  cocoon  and  with 
abdominal  hook-like  spines  for  working  its  way  to  the 
surface  where  it  transforms  to  the  winged  adult  (fig.  6,  J  ; 

fig.  7,  ?)• 

The  adults  of  this  family.  Sesiidae,  have  the  larger  part 
of  one  or  both  pairs  of  wings  free  from  scales  (No.  1172, 
Sesia  thysbe  Fabr).  The  latter  are  found,  however,  on 
the  veins  and  the  edges  of  the  wings.  The  bristles  of  the 
frenulum  in  the  female  are  consolidated  into  one  organ 
as  in  the  male. 

Among  the  frenulum  conservors  are  the  Geometrids 
whose  larvae  appear  to  measure  the  surface  over  which 
they  walk.  It  is  probable  that  the  caterpillars  of  the 
ancient  Geometrids  had  several  pairs  of  prop-legs  like  the 
larvae  of  most  living  Lepicloptera,  but  when  the  Geome- 
trids acquired  the  habit  of  walking  by  looping  the  body, 
there  would  be  no  need  of  any  of  the  prop-legs  excepting 
the  last  pair  or  two  and  disuse  would  tend  to  bring  about 
reduction  and  loss  of  these  organs. 

The  canker  caterpillar,  so  disastrous  to  shade  and  fruit 
trees,  is  a  Geometer.  It  occurs  in  the  spring  form, 
Paleacrita  vernata  Peck,  and  the  fall  form,  Anisopteryx 
pometaria  Harr.  (No.  1173,  $ ,  9  ).  The  position  that 
the  quiet  larva  often  takes  causes  it  to  resemble  a  twig 
and  this  is  doubtless  a  means  of  protection.  When  walk- 
ing it  brings  the  posterior  end  of  its  body  forward  towards 
the  head  end  and  takes  firm  hold  of  the  twig  by  its  prop- 
legs,  thereby  looping  its  body ;  it  then  stretches  out  the 
forward  end  and  takes  hold  by  the  thoracic  legs  when  the 
posterior  part  is  again  brought  forward. 

The  larvae  of  some  of  the  Noctuidae  or  owlet  moths 
do  great  damage  to  grass  and  crops.  One  well  known 
species  is  the  northern  army  caterpillar,  Leucania  uni- 
puncta  Haw.  (No.  1174,  larva  and  adult).  It  is  probable 


METAZOA INSECTA.  463 

that  at  some  remote  time  the  food  supply  of  these  cater- 
pillars failed  and  that  gradually  the  habit  was  acquired 
of  moving  in  companies  toward  fresh  grass  lands  upon 
which  to  feed.  Now  the  habit  has  become  fixed  in  the 
organization  and  is  inherited.  In  this  way  the  army 
caterpillar  has  overcome  conditions  that  would  be  adverse 
to  its  own  preservation. 

Suddenly  a  field  that  has  been  swarming  with  these 
caterpillars  is  wholly  free  from  them.  This  is  owing  to 
the  fact  that  they  have  descended  into  the  ground  where 
their  pupal  life  is  spent. 

Erebus  sfrex  (No.  1175)  is  one  of  the  largest  and 
handsomest  members  of  the  Noctuidae. 

The  extremely  interesting  fact  has  been  proved  by 
Gentry1  that  a  normal  cocoon-builder  under  certain  con- 
ditions may  pass  into  the  pupal  stage  as  a  chrysalis. 
While  the  majority  of  the  larvae  of  the  Noctuid  Acronycta 
oblinita  went  through  their  transformations  in  the  normal 
manner,  at  least  three  without  the  slightest  attempt  at 
cocoon-'making  lay  upon  the  soil  and  after  a  period  of 
five  days  entered  the  chrysalis  state.  Facts  like  this  sug- 
gest the  origin  and  the  evolution  of  the  chrysalis-produc- 
ing butterflies  from  the  cocoon-making  moths. 

The  tussock  moths  or  Lymantriidae  have  become  well 
known  of  late  years  through  their  representative  the 
gypsy  moth,  Porthetria  (  =  Ocneria)  dispar  Linn.  (No. 
1176;  PI.  1177,  figs.  1-6;  Nos.  1178,  1179,  large  speci- 
mens of  the  male  and  female).  A  cluster  of  eggs  covered 
by  yellow  hairs  from  the  body  of  the  female  is  seen  at  the 
left  in  No.  1176  and  in  PI.  1177,  fig.  i,  and  a  few  eggs, 
enlarged,  in  fig.  2.  These  eggs  are  laid  in  July,  August, 
and  September,  on  the  bark  of  trees,  and  the  moth  hiber- 
nates in  the  egg  stage.  The  following  spring  the  cater- 
pillars (No.  1176;  PL  1177,  fig.  3)  are  hatched  and  the 
length  of  larval  life  probably  averages  ten  weeks.  If  the 

iproc.  Acad.  Nat.  Sci.  Phila.,  1875,  p.  25. 


464  SYNOPTIC    COLLECTION. 

temperature  is  favorable,  they  will  search  for  food,  before 
they  are  twenty-four  hours  old.1  They  feed  chiefly  at 
night,  going  up  the  trees  and  out  on  the  branches  after 
dark  and  returning  to  sheltered  places  before  light.  The 
necessity  of  righting  this  insect  intelligently  and  unceas- 
ingly is  evident  when  we  consider  that  it  is  known  to 
destroy  the  foliage  of  nearly  all  trees  and  most  plants  of 
economic  importance.  This  is  most  unusual,  for  though 
the  newly  hatched  Lepidopterous  larva  is  far  less  special- 
ized in  regard  to  its  food  plants  than  the  mature  larva, 
yet  the  latter  as  a  rule  feeds  upon  a  very  restricted  diet. 

The  caterpillar  when  full  grown  becomes  a  pupa  (No. 
1176;  PI.  1177,  fig.  4)  usually  in  July  or  August,  and  in 
from  eight  to  twelve  days  in  Massachusetts  the  pupa 
changes  to  the  moth  (Nos.  1176,  1178,  <?  ;  PI.  1177,  fig. 
5;  Nos.  1176,  1179,  9  ;  PI.  1177,  fig-  6).  It  is  inter- 
esting to  notice  the  difference  in  size  between  the  .well 
fed  specimens  (Nos.  1178,  1179)  and  those  less  for- 
tunate (No.  1176,  specimens  on  the  right).  Within  a  few 
hours  after  emerging  from  the  pupa-case  the  female 
lays  eggs.  The  male  is  a  swift  flier,  but  the  locomotion 
of  the  female  is  limited  to  a  few  struggling  flaps  which 
result  simply  in  lessening  the  force  of  her  fall  from  a 
height.2  She  lays  her  eggs  either  before  this  fall  or  after- 
ward and  then  dies. 

One  of  the  moths  that  winter  in  the  larval  stage  is 
Pyrrhactia  Isabella  Smith  (No.  1180.  larva,  pupa,  cocoon, 
imago),  of  the  family  Arctiidae.  This  is  the  black  and 
reddish  brown  colored  caterpillar  sometimes  seen  crawling 
over  snow.  When  the  larva  is  ready  to  transform  the 
body  shortens  and  apparently  a  thin  gray  veil  slowly 
covers  it  which  grows  thicker  till  the  insect  within  is 


1  Rep.  Mass.  State  Board  Agric.  on  Work  of  Extermination  of 
Gypsy  Moth,  1893,  p.  12  (Senate  document,  No.  6). 

2  Howard,  U.  S.  Dep.  Agric.,  Div.  Ent.,  Bull.  no.  u  (n.  s.),  1897, 
p.  7. 


METAZOA INSECTA.  465 

invisible.  This  covering  or  pupa-case  is  really  formed  of 
the  hairs  thrown  off  by  the  caterpillar  and  these  are  fast- 
ened together  by  silk. 

There  are  scarcely  any  Lepidopterous  insects  that  are 
parasites,  but  Epipyrops  anomala  Westw.,  is  an  exception, 
since  its  caterpillar  (PL  1181,  fig.  i,  cast  skin  of  a  young 
larva;  fig.  2  fully  grown  larva,  dorsal  view;  fig.  3,  ventral 
view)  is  found  attached  to  the  back  of  the  Chinese  lan- 
tern fly,  Hotinus  candelarius  Linn. 

The  body  is  flattened  and  broadened  out  while  the 
legs  are  greatly  reduced  in  size.  When  young  the  larvae 
are  free  from  the  wax  secreted  by  the  Hotinus,  but  as 
they  develop  they  become  entirely  covered  with  it. 

According  to  Westwood  these  parasites  probably  feed 
upon  the  waxy  secretions  of  the  Hotinus.  When  full 
grown  they  drop  off  their  host  and  secrete  "a  cottony 
substance  "  doubtless  made  from  their  waxy  food,  which 
serves  as  a  cocoon  (fig.  4)  for  the  pupa  (fig.  5).  After  a 
variable  time  (from  nine  days  to  upwards  of  twelve 
months)  the  moth  (fig.  6)  escapes. 

Since  Epipyrops  is  an  external  parasite  it  has  not 
undergone  marked  structural  changes  but  its  life  history 
is  unique  among  Lepidoptera. 

The  green  larvae  of  the  hawk  moths  or  Sphingidae 
have  the  habit  of  raising  the  forward  end  of  the  body 
and  holding  it  motionless  for  a  long  time ;  hence  the 
name  of  the  family.  They  feed  on  the  tomato,  potato, 
and  tobacco  plants.  The  common  species  is  Phlegethon- 
tius  celeus  (=  Macro sila  quinquemaculata  Haw.)  (No. 
1182,  larva,  pupa,  and  moth).  The  pupa  is  not  pro- 
tected by  a  cocoon,  but  is  a  chrysalis  with  a  long  han- 
dle-like appendage  which  is  the  case  of  the  sucking  tube. 

The  adult  (No.  1182)  is  a  swifter  flier  than  most  Lepi- 
doptera, and  this  habit  is  correlated  with  the  structure  of 
the  mesothorax  and  metathorax,  these  two  segments  being 
more  closely  consolidated  in  the  hawk  moths  than  in  other 
members  of  the  order. 


466  SYNOPTIC  COLLECTION. 

The  mesothorax  bears  a  pair  of  shoulder  lappets  or 
patagia  which  protect  the  basal  portion  of  the  front  wings. 
Kellogg1  has  pointed  out  that  these  organs  are  small  and 
inconspicuous  in  the  generalized  moths  but  are  remark- 
ably developed  in  these  swift-flying  Sphingidae. 

The  Bombycidae  are  well  known  through  the  silk  made 
by  Bombyx  mori  Linn.  Its  cocoon  (No.  1183)  yields 
the  greater  part  of  the  silk  of  commerce.  This  moth  (No. 
1184)  has  been  domesticated  since  early  times  and  in  con- 
sequence has  almost  wholly  lost  the  power  of  flight.  The 
wings  (PI.  1185,  fig.  i,  fore  wing;  fig.  2,  hind  wing)  of 
the  Bombycidae  are  interesting,  since  the  frenulum  is  in 
a  vestigial  condition,  as  seen  in  Bombyx  mori  Linn.  (fig. 
2,/),  while  the  humeral  angle  of  the  wing  (fig.  2,  //)  is 
becoming  extended  as  in  the  group  of  frenulum  losers 
soon  to  be  described. 

Dr.  A.  S.  Packard  has  pointed  out  in  his  valuable 
memoir  on  Bombycine  moths2  that  the  larvae  of  the  more 
generalized  moths,  the  Noctuidae,  for  example,  are  low- 
feeders  ;  that  is,  they  live  on  grasses  and  low-growing 
plants,  and  that  as  a  rule  they  are  without  spines,  horns, 
tufts,  or  other  ornamentation ;  their  color  is  green  or 
some  quiet  shade.  On  the  other  hand,  the  larvae  of  the 
more  specialized  moths,  like  the  Bombyces,  have  taken 
to  tall  blossoming  plants  or  to  trees.  They  have  become 
adapted  to  their  environment  by  developing  brilliant 
colors  or  varied  ornamentation. 

The  resemblance  often  existing  between  a  caterpillar 
and  its  surroundings  is  illustrated  by  Nerice  bidentata 
Walk.  (PL  1186).  The  saw  like  back  of  this  larva  and 
its  green  color  dashed  with  white  are  in  harmony  with  the 
serrated  margin  and  color  markings  of  the  elm  leaves 
upon  which  it  feeds. 

One  species  of  the   genus  Heterocampa,    (//".  obliqua 


iAmer.  Nat.,  XXIX,  March,  1895,  p.  255. 

2  Mem.  Nat.  Acad.  Sci.,  VII,  Monograph  i,  1895. 


METAZOA INSECTA.  467 

Pack.),  possesses  in  the  young  larval  state  a  pair  of  antler- 
like  horns  (PI.  1187,  fig.  i,  side  view;  fig.  2,  front  view 
of  head  and  prothoracic  horns,  greatly  magnified),  the 
use  of  which  is  unknown.  When  older  the  larva  loses 
these  organs,  as  seen  in  fig.  3. 

Among  the  more  specialized  of  the  Bombycine  moths 
is  Centra  cinerea  Walk.,  in  which  the  anal  prop-legs  have 
become  two  long  tubes  (PI.  1188,  fig.  i),  each  containing 
a  highly  colored  tentacle  or  whip  with  which  Cerura 
lashes  its  body  to  drive  away  its  enemies.1  The  dull-col- 
ored moth  is  seen  in  fig.  2. 

The  American  silk  moth,  Telea  polyphemus  Linn.,  of 
the  family  Saturniidae,  is  a  good  type  form  of  the  group 
of  moths.  The  thoracic  and  abdominal  regions  of  the 
larva  (No.  1189,  larva,  pupa,  cocoon,  and  imago)  are 
large,  while  the  head  is  small.  The  mouth  parts  are  effi- 
cient biting  organs.  The  thoracic  legs  are  weak  but  the 
four  pairs  of  prop-legs  are  strong.  The  caterpillar  spins 
a  cocoon  within  which  the  pupa  remains  motionless  for 
a  longer  or  shorter  time,  according  to  temperature.  Dur- 
ing this  time  its  appendages  are  encased  in  sheaths  and 
are  fastened  closely  to  the  body.  When  ready  to  trans- 
form, the  pupa  secretes  a  liquid  which  dissolves  the  gluey 
substance  holding  the  silken  threads  together,  so  that 
the  pupa  emerges  without  doing  great  damage.'2 

The  moth  (No.  1189)  has  a  robust  body,  the  thorax 
being  the  largest  part.  The  three  regions  are  not  closely 
connected,  and  the  junction  of  the  thorax  with  the  abdo- 
men is  broad. 

The  antennae  are  either  thread-like  or  feather-like,  and 
as  a  rule  these  organs  in  the  male  are  much  broader  than 
in  the  female.  The  mouth  parts  are  vestiges  and  the 


1  Scudder.  Trans.  Amer.  Ent.  Soc.  Phila.,  1877,  p.  77. 

2  Trouvelot  states    the    adult   escapes  without    breaking    a  fiber. 
Comstock    says,    "and   breaking  the  threads,"   the    adult    escapes 
through  the  large  round  hole. 


468  SYNOPTIC    COLLECTION. 

food  is  obtained  by  lapping.  The  fore  wings  are  large, 
while  the  hind  wings  are  reduced  in  size,  and  there  is  a 
corresponding  reduction  in  the  metathoracic  segment. 
The  frenulum  is  now  wholly  lost,  and  the  humeral  angle 
is  large.  Both  pairs  of  wings  are  held  in  a  drooping 
position  when  the  insect  is  resting. 

The  remaining  families  of  moths,  skippers,  and  butter- 
flies are  grouped  together  as  frenulum  losers.  In  place 
of  the  frenulum  they  have  a  greatly  extended  humeral 
angle  of  the  hind  wings  which  passes  under  the  fore  wing, 
as  already  stated,  and  ensures  unity  of  action  in  the  two 
wings. 

The  Saturniidae  include  some  of  our  largest  and  most 
beautiful  moths,  such  as  the  Luna,  Actias  luna  Linn., 
(No.  1190).  The  great  Cecropia,  Samia  cecropia  Linn., 
(Nos.  1191,  1192)  suspends  her  cocoon  (No.  1191)  like 
a  cradle,  while  the  Promethea  moth,  Callosamia  promethea 
Drury  (Nos.  1193,  1194),  hangs  hers  from  a  twig. 

Among  the  varied  habits  of  larvae  that  of  the  apple- 
tree  tent  caterpillar,  Clisiocampa  americana  Harr.  (No. 
1195,  eggs,  larva,  cocoon,  pupa,  moth)  is  interesting. 
These  social  larvae  spin  a  tent  and  live  together  in  great 
numbers.  They  leave  the  tent  to  feed  but  return  to  it 
when  satisfied. 

Urbiculae.  The  skippers  resemble  moths  in  certain 
features,  while  in  other  respects  they  are  like  butter- 
flies. The  larvae  have  the  general  characters  common 
to  both  moths  and  butterflies,  while  they  differ  from 
those  of  both  groups  by  having  a  large  prominent 
head  and  a  well  developed  prothorax  (PL  1196,  fig.  i, 
Epargyreus  tityrus  Fabr.).  On  the  dorsal  side  of  this 
segment  there  is  a  horny  shield.  The  pupae  (fig.  2)  are 
rounded  like  those  of  moths  and  the  pupal  stage  is  passed 
in  a  frail  cocoon  made  of  leaves  lined  thinly  with  silk 
(fig.  2).  This  pupa,  however,  is  not  free  within  its 
cocoon  but  is  fastened  by  means  of  a  hook  or  cremaster 
at  the  posterior  end  of  its  body  to  a  Y-shaped  thread 


METAZOA INSECTA.  469 

while  the  opposite  end  of  the  body  is  held  in  the  loop  of 
a  second  Y-shaped  thread  (fig.  2). 

The  adults  (No.  1 197)  have  the  robust  body  of  moths. 
The  head  is  broad  and  the  antennae  are  usually  thread- 
like but  are  enlarged  near  the  end,  though  the  tip  curves 
backward  like  a  hook.  The  sucking  tube  in  these  insects 
is  remarkably  long. 

Skippers  fly  by  day  ;  a  few  hold  their  wings  when  at 
rest  in  a  horizontal  position,  while  some  hold  the  hind 
wings  in  this  way  and  the  fore  wings  erect ;  most,  how- 
ever, hold  their  wings  erect  like  the  butterflies  next  to  be 
described. 

Papilionidae  or  swallow-tails.  This  family  includes  the 
more  generalized  butterflies.  The  caterpillars  of  the 
swallow-tails  (No.  1198,  Papilio  asterias,  dorsal  view;  No. 
1199,  side  view)  are  naked,  being  without  spines  or  con- 
spicuous hairs.  They  have  two  processes  on  the  pro- 
thorax  called  osmateria  which  can  be  thrown  out  and 
withdrawn,  and  since  they  give  out  a  disagreeable  odor 
are  supposed  to  be  organs  of  defence. 

The  pupa  (No.  1198),  now  called  the  chrysalis,  is 
angular  and  not  rounded  like  that  of  the  moth.  It  is 
without  a  cocoon  but  is  covered  by  the  dry,  hardened 
skin  of  the  larva  ;  it  hangs  suspended  by  the  tail  and  a 
loose  girt  around  the  middle. 

The  adult  (No.  1198)  has  a  slender  body  very  different 
from  that  of  the  moth.  The  antennae  are  knobbed  at 
their  ends  without  a  recurved  hook.  The  three  pairs  of 
thoracic  legs  are  well  developed.  These  insects  fly  by  day 
and  when  at  rest  hold  their  wings  erect.  The  Papilioni- 
dae can  be  easily  distinguished  from  other  butterflies  by 
the  prolongation  of  the  hind  wings. 

Pieridae.  Our  most  common  white  and  yellow  butter- 
flies belong  to  the  Pieridae.  The  larva  of  the  cabbage 
butterfly,  Pieris  rapae  Schrank  (No.  1200  larva,  chry- 
salis, £  ;  No.  1201,  9)  is  a  naked  green  caterpillar. 
The  chrysalis  is  suspended  in  the  same  way  as  that  of 


470  SYNOPTIC    COLLECTION.  - 

the  Papilionidae.  The  sexes  of  the  adult  can  be  distin- 
guished by  the  black  rounded  spots  on  the  fore  wing,  the 
male  (No.  1200)  having  one  spot  and  the  female  (No. 
1201)  two.  PL  1202  will  be  referred  to  farther  on  when 
speaking  of  the  development  of  the  wings. 

Lycaenidae  or  gossamer-winged  butterflies'.  The  cater- 
pillars of  this  family  remind  one  of  the  Eucleidae  among 
the  moths.  The  body  is  slug-like  and  the  thoracic  legs 
and  prop-legs  are  not  seen  from  above.  In  fact,  the 
prop-legs  are  so  small  in  some  species,  as  in  the  American 
copper,  Heodes  hypophlaeas  Scudd.  (No.  1203),  that,  ac- 
cording to  Scudder1  they  can  be  readily  detected  only 
when  the  skin  of  the  caterpillar  is  prepared  by  inflation. 
The  chrysalis  of  Heodes  hypophlaeas  Scudd.,  is  suspended 
by  the  tail  and  the  loop  around  the  middle,  but  the  latter 
is  drawn  much  tighter  than  in  the  Papilionidae.  The 
adult  shows  a  tendency  in  the  male  towards  a  reduction 
of  the  fore  legs,  but  in  the  female  the  three  pairs  are 
useful  and  similar  in  structure  as  in  the  Papilionidae, 
skippers,  and  moths. 

Most  caterpillars  feed  upon  vegetable  food,  as  we  have 
already  seen,  but  the  wanderer,  Feniseca  tarquinius  Grote. 
belonging  to  the  Lycaenidae,  is  an  exception  to  the  rule, 
since  it  is  carnivorous,  living  wholly  upon  Aphides. 

The  larva  of  the  spring  azure,  Cyaniris  pseudargiolus 
Bd.  and  Lee.  (No.  1204)  is  provided  with  tubes  on  the 
seventh  and  eighth  abdominal  segments  which  secrete 
honey  that  is  keenly  relished  by  ants,  so  that  these  latter 
insects  usually  attend  the  caterpillars. 

According  to  Comstock,  Cyaniris  exhibits  polymor- 
phism to  the  greatest  degree  of  any  known  species,  as 
many  as  nine  or  ten  forms  having  been  discovered. 

Thecla  (No.  1205)  is  one  of  the  hair-streaks  which 
with  the  blues  and  coppers  make  up  the  Lycaenidae. 
These  are  all  small  in  size  and  delicate  in  organization. 

1  Butterflies,  1881,  p.  19. 


METAZOA INSECTA.  471 

Nymphalidae  or  brush  footed  butterflies,  A  typical  form 
of  each  of  the  large  orders  of  insects  so  far  described  has 
been  given,  and  now  one  of  the  Nymphalidae  is  chosen 
to  represent  the  order  of  Lepidoptera.  The  milkweed 
butterfly,  Danais  plexippus  Linn.  (Nos.  1206-1208)  com- 
bines many  of  the  essential  characters  of  the  order.  Its 
egg  (PI.  1206,  fig.  i),  like  that  of  many  Lepidoptera,  is 
symmetrical  and  highly  ornamented.  The  caterpillar 
(No.  1207  ;  PI.  1206,  fig.  2)  has  the  cylindrical  segmented 
body  of  most  young  Lepidoptera.  Even  in  its  earliest 
stage  it  has  this  secondary  or  caterpillar  form,  the  primi- 
tive Thysanuriform  larval  stage  being  wholly  skipped. 
In  its  biting  mouth  parts,  however,  the  caterpillar  resem- 
bles the  generalized  insects.  The  three  pairs  are  present, 
the  mandibles  (PL  1206,  fig.  3,  md)  being  strong  and 
well  developed.  Attached  to  the  second  pair  of  maxillae 
is  the  horny  tube,  the  spinneret  (fig.  3,  j),  by  means  of 
which  the  insect  spins  the  silken  attachment  that  suspends 
the  chrysalis. 

The  thorax  bears  the  three  pairs  of  jointed  legs,  each 
ending  in  a  hook.  It  has  also  been  found  that  the  meso- 
thorax  and  metathorax  of  the  caterpillar  bear  the  rudi- 
ments of  wings  beneath  the  outer  skin.  These  are  in- 
dicated, according  to  Gonin,1  by  a  bagging  inward  of 
the  hypodermis  (PL  1202,  fig.  i,  Pieris  brassicae,  before 
the  first  moult).  These  rudiments  develop  as  shown  by 
fig.  2,  which  is  the  wing-rudiment  of  the  full-grown  larva 
with  its  trachea  and  branches.  By  dissecting  away  the 
body  wall  just  before  pupation,  the  crumpled  wings  may 
be  seen  as  in  fig.  3.  The  existence  of  these  appendages 
in  the  larva  demonstrates  more  forcibly  than  almost  any 
other  discovery  possibly  could,  a  fact  difficult-  for  most 
people  to  grasp  fully ;  namely,  that  the  caterpillar  is  a 
young  butterfly. 

It  is  seen  that  the  time  for  acquiring  these  rudiments 

1  See  also  Mayer,  Bull.  Mus.  Comp.  Zool.,  XXIX,  no.  5,  1896. 


472  SYNOPTIC    COLLECTION. 

has  been  carried  back  from  the  pupal  stage  to  the  early 
life  of  the  larva  which  is  what  we  should  naturally  expect 
to  find  in  the  specialized  orders  of  insects. 

The  abdomen  is  provided  with  five  pairs  of  fleshy  prop- 
legs,  each  supplied  with  many  hooks. 

According  to  Scudder  the  bright  colors  of  the  young 
Danais  may  be  considered  as  warning  colors  indicating 
the  unpalatable  nature  of  the  animal.  While  this  cater- 
pillar is  without  tubercles,  it  has  a  pair  of  fleshy  filaments 
extending  from  the  anterior  and  posterior  parts  of  the 
body  that  are  not  present  in  the  young  larva  but  which 
develop  in  the  process  of  growth. 

The  mature  larva  fastens  itself  by  the  tail  only,  the 
girt  around  the  middle  being  no  longer  necessary,  and 
transforms  to  the  beautiful  bright  green  chrysalis  (No. 
1207  ;  PI.  1206,  fig.  4)  marked  by  brilliant  golden  spots. 
The  appendages  are  encased  in  sheaths  and  fastened  to 
the  body. 

The  adult  (No.  1207,  9  )  has  a  cylindrical  body  cov- 
ered with  a  coating  of  hairs  and  scales.  When  this  coat- 
ing is  removed,  the  three  regions  are  found  to  be  somewhat 
loosely  connected  and  the  mesothorax  and  metathorax  (PI. 
1206,  fig.  5),  although  more  complex  than  in  most  of  the 
generalized  insects,  are  still  capable  of  considerable 
motion. 

The  head  is  freely  movable,  although  in  a  lesser  degree 
than  that  of  dragon-flies.  This  freedom  is  partly  due  to 
the  free  prothorax  which  in  the  Lepidoptera  is  reduced, 
as  we  have  already  seen,  to  a  mere  collar-like  segment 
(fig.  7,/;  see  also  fig.  5).  The  deep  groove  between  the 
mesothorax  (fig.  7,  ms)  arid  metathorax  (fig.  7,  mt\ 
shaded  in  fig.  5),  and  the  power  possessed  by  these  two 
segments  of  moving  upon  each  other  are  probably  due  to 
the  peculiar  wave-like  motion  of  the  insect  which  is  in 
striking  contrast  to  the  swift,  arrow-like  flight  of  the 
dragon-fly. 

The  compound  eyes  constitute  about  two  thirds  of  the 


METAZOA INSECTA.  473 

head;  there  are  no  ocelli,  though  each  compound  eye  is 
made  up  of  an  immense  number  of  single  eyes. 

The  antennae  (No.  1207  ;  PI.  1206,  fig.  7)  are  knobbed, 
the  typical  character  of  butterflies,  as  already  stated. 

Remarkable  modifications  in  structure  have  taken  place 
in  the  mouth  parts,  suggestive  of  equally  great  changes 
in  the  habits  of  these  insects  in  some  remote  past. 

The  mandibles  described  in  the  young  butterfly  have 
become  obsolete,  consisting  only  of  tiny  plates  (PL  1206, 
fig.  6,  md)  immovably  fastened  to  the  head.  The  first 
pair  of  maxillae  has  taken  upon  itself  the  function  of 
sucking  nectar  from  the  corollas  of  flowers,  and  has 
become  a  long  spiral  organ  (fig.  7,  mx'}.  The  palpi  (fig. 
7 1/")  °f  the  second  pair  of  maxillae  have  become  brushes 
for  aiding  the  insect  in  obtaining  nectar. 

The  reduction  of  the  prothorax  indicates  that  the  first 
pair  of  legs  are  of  little  or  no  use,  and  this  is  the  case, 
since  they  do  not  even  support  the  insect  when  it  alights 
but  are  folded  across  the  breast.  The  first  section  is 
supplied  thickly  with  hairs,  hence  the  name  of  Nympha- 
lidae  or  brush-footed  butterflies.  The  remaining  legs  are 
weak  and  are  of  no  service  in  locomotion  but  simply  in 
supporting  the  insect. 

The  chief  character  of  the  wings  is  the  coating  of  scales 
which  are  modified  hairs.  This  peculiarity  has  given  the 
order  the  name  of  Lepidoptera,  meaning  scale  and  wing. 
These  scales  are  striated  and  of  different  colors ;  each  is 
attached  by  a  stem  or  pedicel  and  their  arrangement  on 
the  wing  is  like  that  of  shingles  on  a  house. 

According  to  Mayer1  the  wings  of  Danais  plexippus 
Linn.,  during  early  pupal  life,  are  transparent  as  glass, 
and  this  condition  corresponds  to  the  period  before  the 
scales  are  formed.  From  five  to  ten  days  before  emer- 
gence the  wings  become  opaque  and  white.  This  condi- 
tion is  caused  by  the  withdrawal  of  the  protoplasm  from 

1Bull.  Mus.  Comp.  Zool.,  XXIX,  no.  5,  1896,  p.  209. 


474  SYNOPTIC    COLLECTION. 

the  scales,  leaving  them  as  little  hollow  bags  filled  with 
air.  After  this  a  dull  ochre  yellow  or  drab  color  suffuses 
the  wing  excepting  where  the  white  spots  of  the  mature 
wing  are  to  be  (see  PL  1208,  fig.  i).  This  color  is  due 
to  the  fact  that  after  the  protoplasm  has  left  the  scales 
the  "blood"  or  haemolymph  enters  them  and  changes  to 
an  ochre  yellow  and  finally  to  a  drab.  About  twenty-four 
hours  later  the  mature  colors  gradually  develop,  appear- 
ing first  between  the  nervures  or  veins  (figs.  2,  3)  and 
finally  on  the  nervures  and  anterior  margin  (fig.  4). 
These  colors  are  due  to  chemical  changes  taking  place  in 
the  haemolymph  itself. 

It  is  interesting  to  note  that  ochre  yellow  and  drab 
tints  which  appear  first  after  the  white  are  the  shades 
peculiar  to  the  more  generalized  nocturnal  moths,  while 
the  brilliant  colors  which  are  the  result  of  more  complex 
chemical  processes  are  found  in  the  specialized  diurnal 
butterflies. 

When  the  insect  is  resting,  the  wings  are  held  in  an 
erect  position  over  the  back. 

The  power  for  sustained  flight  possessed  by  Danais  is 
exceptional.  It  migrates  southward,  flying  long  distances 
in  flocks  numbering  hundreds  of  thousands.  It  has  also 
been  seen  at  sea  five  hundred  miles  from  land  (Scudder). 

Besides  the  legs  and  wings  there  are  a  pair  of  shoulder 
lappets  or  patagia  attached  to  the  mesothorax  which  pro- 
tect the  hinge  of  the  anterior  wing  from  injuries.  These 
we  have  already  seen  in  the  hawk  moths. 

The  male  is  distinguished  from  the  female  by  the  black 
patch  next  one  of  the  veins  near  the  middle  of  the  hind 
wings.  This  patch  is  really  a  little  pocket  containing 
specialized  scent  scales  or  androconia. 

The  family  Nymphalidae  includes  many  genera.  Liby- 
thea  carinenta  Cram.  (No.  1209)  is  remarkable  for  having 
long  palpi  which  extend  forward  in  the  form  of  a  beak. 
Heliconius  charitonius  Linn.  (No.  1210)  is  conspicuously 
colored,  while  the  mourning  cloak,  Vanessa  antiopa  (No. 


METAZOA INSECTA.  475 

12 1 1)  has  deep,  rich  hues  and  is  one  of  our  common  New 
England  butterflies. 

One  of  the  most  magnificent  genera  is  Morpho,  some  of 
whose  species  are  regal  in  their  coloring.  Morpho 
epistrophis  Hiibn.  (No.  1212)  is  an  exquisite  light  blue 
species. 


Order  15.  —  HYMENOPTERA. 

The  Hymenoptera  and  the  following  order,  the  Diptera, 
are  extremely  interesting,  since  the  former  illustrate  better 
than  any  other  order  of  insects  specialization  by  addition, 
and  the  latter  ^specialization  by  reduction. 

Partly  because  of  the  many  adaptive  organs  possessed 
by  Hymenoptera  and  partly  on  account  of  their  remark- 
able physiological  development,  reaching  in  the  case  of 
ants  an  intelligence  which  differs  from  that  of  man  only 
in  degree  and  not  in  kind  (Lubbock),  the  order  Hymen- 
optera has  been  placed  by  many  entomologists  at  the  head 
of  the  insect  group.  In  a  natural  classification,  however, 
it  is  evident  that  that  order  of  insects  which  is  farthest 
removed,  both  in  its  larval  and  adult  structural  features, 
from  the  primitive  ancestral  stock-form  is  the  one  entitled 
to  the  position  of  the  most  specialized  of  its  kind.  It 
will  be  seen  (p.  493)  that  the  young  and  full  grown  Dip- 
tera are  unquestionably  farther  removed  from  the  Thy- 
sanuriform  type  of  insect  than  these  stages  of  other  orders 
and  for  this  reason  the  Diptera  are  placed  last  in  our 
Synoptic  Collection  of  insects  as  representing  the  acme 
of  specialization. 

Ttrcbrantia,  or  boring  Hymenoptera.  The  larvae  of  the 
Hymenopterous  family  of  saw-flies,  Tenthredinidae,  are 
caterpillar-like  in  form  and  general  characters,  as  seen  in 
the  violet  sawfly,  Emphytus  canadensis  Kby.  (PI.  1213, 
fig.  i,  x  4).  The  active  larva  is  provided  with  biting 
mouth  pirts,  jointed  thoracic  legs,  and  eight  pairs  of  prop 


476  SYNOPTIC    COLLECTION. 

legs.  The  cocoon  (fig.  2)  is  spun  by  the  larva  for  the 
protection  of  the  pupa  (fig.  3).  In  these  ways  the  gener- 
alized Hymenoptera  prove  their  kinship  with  the  Lepi- 
doptera. 

The  adult  Emphytus  (fig.  4)  has  a  robust  body  and 
the  junction  of  the  thorax  and  abdomen  is  broad,  as  in 
the  generalized  Lepidoptera.  The  mouth  parts  are  spe- 
cialized by  addition,  being  adapted  for  biting  and  sucking. 
The  two  pairs  of  wings  are  membranous  with  few  veins, 
and  the  posterior  pair  is  much  smaller  than  the  forward 
pair.  The  ovipositor  has  become  modified  into  a  pair  of 
saws  by  means  of  which  the  insect  makes  holes  in  leaves 
wherein  its  eggs  are  deposited. 

Many  of  these  characters  are  more  plainly  seen  in  one 
of  our  largest  sawflies,  Cimbex  americaria  Leach  (No. 
1214),  and  the  saws  of  Cimbex  sylvarum  are  figured  in 
PI.  1215.  Here  they  are  spread  out  horizontally  and  the 
toothed  edges  of  the  saws  are  seen  on  the  outer  side. 

Another  generalized  family  of  the  Hymenoptera  is  the 
Siricidae  or  horntails.  The  larvae  of  these  insects,  how- 
ever, show  marked  adaptation  of  structure  to  habit.  For 
instance,  the  larva  of  Tremex  columba  Linn,  lives  in  wood 
and  this  habitat  has  brought  about  a  reduction  in  the  size 
of  the  legs  and  a  loss  of  the  prop-legs,  causing  the  insect 
to  resemble  the  wood-inhabiting  larvae  of  the  Coleoptera. 
The  pupa  is  protected  by  a  cocoon  of  silk  and  wood 
chips. 

The  adult  (No.  1216)  has  a  sessile  abdomen  like  the 
sawflies.  The  ovipositor,  in  this  case,  is  a  boring  imple- 
ment instead  of  a  saw,  and  it  is  used  for  boring  holes  in 
trees  in  each  of  which  an  egg  is  deposited. 

Cynipidae.  It  has  been  pointed  out  by  Dr.  Adler1  that 
the  galls  of  Cynipidae  may  be  arranged  in  groups  of  con- 
stantly increasing  complexity,  beginning  with  those  like 

'Oak  Galls  and  Gall  Flies,  1894;  English  transl.  by  Straton,  p. 
xxxiii. 


METAZOA INSECTA.  477 

Spathcgaster  baccarum  Linn.  (PI.  1217,  figs,  i,  2),  and 
leading  up  to  the  complicated  structure  of  Cynips  kollari 
Hartig  (No.  1218,  complex  gall  of  Cynips;  No.  1219, 
young  and  adult  Cynips  quercus  spongifica  O.  S.).  In 
Spathegaster  the  simple  gall  (PI.  12 17,  on  oak  leaf  and 
the  peduncle  of  the  flowering  catkin  of  the  oak)  consists 
of  nutritive  tissue  enclosed  in  thin-walled  parenchyma, 
while  in  Cynips  the  gall  has  an  inner  gall  enclosed  in 
thick-walled  parenchyma,  surrounded  by  spongy  tissue  and 
covered  by  a  differentiated  epidermis.  The  gall  is  an 
abnormal  growth  of  the  plant  caused  by  animal  agency 
working  from  within  (Adler). 

The  female  punctures  the  oak  leaf  and  deposits  her 
egg,  but  the  gall  does  not  begin  to  develop  until  the  larva 
is  hatched.  It  is  therefore  through  the  agency  of  the 
young  gall-fly  that  the  plant  is  excited  into  active  gall- 
growth.  "The  moment  the  larva  has  for  the  first  time 
wounded  the  surrounding  cells  with  its  delicate  mandibles, 
a  rapid  cell  growth  begins."1 

The  larva  spends  its  whole  life  within  the  narrow  con- 
fines of  the  gall.  Having  little  need  of  antennae  and  legs, 
these  organs  exist  as  vestiges.  The  pupal  stage  is  also 
passed  in  the  home  of  the  larva,  and  the  adult  fly  (No. 
1219)  makes  a  hole  in  the  outer  wall  in  order  to  escape. 

These  insects  illustrate  alternation  of  generations,  since 
the  brood  of  the  first  generation  (the  spring  gall  flies, 
Cynips  quercus  spotigifica  O.  S.)  is  made  up  of  males  and 
females,  while  that  of  the  second  generation  (the  fall  gall 
flies,  Cynips  quercus  aciculata  O.  S.)  is  composed  wholly 
of  agamous  females. 

The  parasitic  Hymenoptera  seem  to  be  more  nearly 
related  to  the  Terebrantia  already  described  than  to  the 
next  division  of  Hymenoptera,  the  Aculeata,  and  for  this 
reason  they  are  now  considered.  All  the  species  of  the 
immense  family  of  Ichneumonidae  are  parasites,  destroy- 

1  Adler,  loc.  cit .,  p.  101. 


478  SYNOPTIC    COLLECTION. 

ing  either  the  eggs,  larvae,  pupae,  or  adults  of  other 
insects,  and  in  this  way  proving  more  beneficial  to  man 
than  almost  any  other  group.  It  is  indeed  singular  that 
a  whole  family  should  take  upon  itself  so  completely  the 
parasitic  habit ;  and  since  this  habit  is  far  removed  from 
the  primitive  habits  of  primitive  insects,  so  the  structure 
of  these  parasites  is  very  different  from  that  of  their 
Thysanuran  ancestors. 

Thalessa  lunator  Fabr.  (No.  1220,  9  ;  No.  1221,  g) 
is  one  of  our  largest  species.  The  extremely  long  ovi- 
positor of  the  female  (No.  1220),  measuring  from  three  to 
five  inches,  consists  of  three  parts  and  is  encased  in  a 
sheath  made  of  two  parts.  By  means  of  this  awl-like 
organ  Thalessa  reaches  the  burrow  of  the  horntail,  Tremex 
cohimba  Linn,  and  deposits  its  egg.  The  footless  larva 
on  hatching  attaches  itself  to  the  Tremex  larva  and  sucks 
its  blood.  According  to  one  observer  quoted  by  Lintner1 
Thalessa  has  been  seen  "sitting  upon  the  bark  where  per- 
forations mark  the  exits  of  previous  occupants  and  also 
running  around  until  she  finds  a  promising  spot,  as,  for 
instance,  the  hole  made  by  a  Tremex  in  depositing  her 
eggs."  This  hole  she  sometimes  takes  advantage  of, 
probing  it  with  her  ovipositor  until  the  burrow  is  reached. 
Riley  has  shown  that  the  instinct  which  guides  Thalessa 
to  a  Tremex  burrow  is  not  unerring,  but  more  or  less 
experimental  work  is  done  and  often  mistakes  are  made. 

Those  ichneumons  that  lay  their  eggs  in  caterpillars 
and  the  like  do  not  need  long  ovipositors  and  therefore 
this  organ  is  shortened  (No.  1222,  Ichneumon  grandis 
Brulte). 

The  social  Hymenoptera  or  the  wasps,  bees,  and  ants, 
are  remarkable  animals  when  considered  from  a  physio- 
logical point  of  view.  Their  skill,  intelligence,  and  their 
power  to  improvise  implements  and  use  them,  challenge 
the  profoundest  thought  of  the  biologist.  Among  all  the 

!4th  Rep.  Ins.  N.  Y.,  1888,  p.  38. 


METAZOA INSECTA.  479 

animals  so  far  described,  the  social  instinct  reaches  its 
most  complete  development  in  the  ants.  This  commu- 
nistic life  of  the  social  Hymenoptera  has  been  brought 
about  by  the  specialization  of  certain  individuals  which 
started  as  solitary  insects  of  either  the  male  or  female 
sex.  It  has  doubtless  required  a  long  period  of  time  and 
a  vast  number  of  generations  to  bring  this  social  organiza- 
tion to  such  a  state  of  efficiency  as  we  find  it  to-day.  If 
mental  qualities  were  made  the  basis  of  our  classification, 
ants  would  not  only  be  the  most  specialized  of  insects  but 
would  come  nearer  to  man  than  the  ape  (Lubbock).  It 
is  obvious,  however,  that  such  a  classification  would  not 
represent  the  genealogical  succession  of  animals  upon  our 
earth ;  such  a  succession,  it  must  be  borne  in  mind,  can 
be  determined  only  by  a  knowledge  of  the  structure  and 
the  development  of  animals. 

The  species  of  solitary  wasps  far  outnumber  the 
social  species  in  the  United  States.  The  fossorial  or 
digger  wasps  are  solitary  in  their  habits  and  are  either 
male  or  female.  Like  most  insects,  also,  their  life  is  so 
short  that  as  a  rule  they  neither  see  nor  care  for  their 
young,  although  the  preparation  they  make  for  them  is 
exceptional  in  its  character. 

Pepsis  caerulea  Linn.  (No.  1223),  one  of  the  Pompilidae, 
is  a  robust  insect  with  the  thorax  attached  to  the  abdomen 
by  so  short  a  peduncle  that  it  is  sometimes  described  as 
having  none.  Its  mandibles  are  large,  strong  organs, 
and  these  together  with  the  fore  and  hind  pairs  of  legs 
are  adapted  for  digging  burrows  in  the  ground,  in  each 
one  of  which  an  egg  is  placed.  This  habit  is  no  new 
feature  of  insect  economy,  but  what  is  unique  is  the  knowl- 
edge the  parent  possesses  of  paralyzing  insects  without 
killing  them.  She  must  provide  sufficient  animal  food 
for  the  entire  life  of  her  young ;  if  the  spiders,  caterpillars, 
and  the  like  were  killed  they  would  soon  be  unfit  for  food; 
therefore  she  thrusts  her  powerful  sting  and  poison  into 
the  nerve  centers  of  the  particular  animal  her  larva  feeds 


480  SYNOPTIC    COLLECTION. 

upon  and  renders  it  motionless.  With  these  paralyzed 
animals  she  stocks  the  burrow ;  she  then  deposits  an  egg 
and  closes  it.  When  every  egg  is  laid  her  life  work  is 
accomplished.  No  one  can  read  the  admirable  observa- 
tions and  experiments  of  the  Peckhams1  without  feeling 
that  the  solitary  wasps  offer  remarkable  instances  of 
inherited  instinct  and  of  reasoning  intelligence.  It  is 
interesting  to  note  that  the  inherited  instinct  is  much 
more  flexible  than  has  been  generally  supposed,  and  is 
often  modified  by  individual  judgment  and  experience. 

Sphex  ichneumonea  Linn.  (No.  1224  9  ;  No.  1225,  <£), 
another  fossorial  and  solitary  wasp  has  the  thorax  fas- 
tened to  the  abdomen  by  a  slender  peduncle,  the  length 
of  which  varies  in  different  species.  The  female  stocks 
her  burrow  with  the  green  grasshopper,  Orchelimum 
vulgar e  (No.  1027). 

The  solitary  wasp,  Odynerus,  makes  its  nest  (No. 
1226)  of  clay  while  other  species  of  this  genus  fill  up 
key  holes  and  the  like. 

The  most  specialized  of  the  solitary  wasps  are  the 
Mutillidae.  The  thorax  in  the  winged  males  (No.  1227, 
Mutilla  occidentalis]  exhibits  the  suture  between  the  three 
segments  as  in  most  insects,  but  in  the  wingless  females 
these  sutures  have  become  obliterated.  This  consolidated 
and  sutureless  condition  is  evidence  of  specialization  by 
reduction  and  is  suggestive  of  the  evolutionary  history 
through  which  this  species  has  passed. 

The  most  simple  social  conditions  are  found  in  the 
beginnings  of  a  colony  where  the  female  makes  a  nest, 
lays  her  eggs,  and  instead  of  dying,  lives  on  and  works, 
taking  upon  herself  the  entire  care  of  the  young,  doing 
all  the  tasks  incident  to  family  life,  until  the  first  brood 
of  young  (which  are  all  females  specialized  by  reduc- 


1  Instincts  and  Habits  of  the  Solitary  Wasps,  by  George  W.  and 
Elizabeth  G.  Peckham,  Wisconsin  Geol.  and  Nat.  Hist.  Survey, 
Bull.  no.  2  (Sci.  Ser.,  no.  i).  1898. 


METAZOA INSECTA.  481 

tion  and  called  workers)  are  old  enough  to  assume  the 
responsibility  of  carrying  on  the  industrial  work  of  the 
nest  and  of  providing  in  their  turn  for  their  mother.  She 
then  gives  up  the  many  activities  in  which  she  has  been 
engaged  and  devotes  herself  wholly  to  one  object,  that  of 
increasing  the  size  of  the  family  which  now  may  be  called 
a  colony.  In  this  colony  there  are,  besides  herself  who 
is  now  the  queen,  males  and  workers.  The  males  take 
no  part  whatever  in  the  industrial  employments  of  the 
nest  and  are  apparently  unaware  of  them  (Sharp). 
There  is  no  distinct  line  of  demarcation  between  the 
worker  and  queen,  such  as  we  shall  find  farther  on  in  the 
social  bees,  although  the  development  of  the  reproductive 
organs  of  the  worker  has  been  in  a  measure  suppressed. 

The  larva  of  most  of  the  social  wasps  is  a  colorless, 
legless  grub  which  lies  head  downward  in  the  cell  of  the 
nest.  It  is  held  in  this  position  when  young  by  a  sticky 
secretion  ;  later  the  enlarged  anterior  end  of  the  body 
just  fits  the  opening  and  holds  the  insect  in  place.  It  is 
fed  on  prepared  food,  but  the  pupa  stage  is  quickly 
reached  and  soon  passed,  and  the  adult  (No.  1228,  Polis- 
tes  metricus  Say)  comes  forth  armed  and  equipped  for 
work.  It  makes  its  nest  (No.  1229)  which  consists  of  a 
single  layer  of  cells  without  an  external  covering.  The 
material  of  the  nest  is  obtained  by  scraping  weather- 
beaten  wood  with  the  mandibles,  chewing  it,  and  mixing  it 
with  the  saliva.  In  each  cell  an  egg  is  laid  and  when  the 
young  are  hatched  they  are  fed  by  the  females  and  workers 
on  the  sweet  juices  of  flowers  and  fruits  besides  some 
well  masticated  solid  food. 

One  of  the  most  social  wasps  is  Vcspa  metadata  Linn. 
(No.  1230,  larva;  No.  1231,  $  ;  No.  1232,  9  ;  No. 
I233?  ?  )•  Its  papery  nest  (No.  1234)  is  made  of  rows  of 
cells,  one  placed  below  the  other,  and  protected  by  a 
thick  outer  covering.  These  nests  vary  in  size,  a  large 
one  in  my  possession  measuring  forty-two  by  fifty-one 
inches  in  circumference.  These  nests  are  used  only  one 


482  SYNOPTIC    COLLECTION. 

season.  In  the  autumn  the  males  and  workers  die,  while 
the  females  leave  the  nest  and  hibernate  in  sheltered 
places  till  spring  comes,  when  they  found  new  colonies. 

Apidae.  There  are  solitary  bees  like  Prosopis  (PI. 
1235,  P.  signatus)  which  are  much  less  specialized  than 
the  social  bees.  The  body  is  nearly  naked.  The  probos- 
cis is  short  and  the  hind  pair  of  legs  are  not  modified  but 
are  similar  to  the  other  two  pairs.  These  bees  are  either 
male  or  female,  like  most  other  insects,  and  like  the  soli- 
tary wasps  they  do  not  live  to  care  for  their  young. 

There  are  also  semi-social  bees  like  the  humble  bee, 
Bombus americana  (No.  1236).  The  female  of  this  genus, 
like  that  of  the  generalized  wasps,  makes  and  provisions 
the  nest,  consisting  of  a  few  cells,  lays  the  eggs,  and  cares 
for  the  young  until  enough  workers  have  grown  to  per- 
form the  necessary  industrial  labor  of  the  little  colony ; 
then  she,  as  queen,  devotes  herself  to  one  special  occupa- 
tion, that  of  egg-laying.  It  is  interesting  to  note  that  the 
workers  of  this  genus  are  slightly  differentiated  from  the 
females,  and  it  would  seem  as  if  here  we  had  an  evolu- 
tionary stage  between  the  wholly  undifferentiated  female 
of  the  most  generalized  bees  and  the  extremely  modified 
worker  of  the  specialized  genera.  The  colony  of  Bombus 
survives  only  one  season  ;  a  few  females  hibernate  and 
start  new  colonies  in  the  spring. 

The  most  social  of  all  bees  is  the  domesticated  honey 
bee,  Apis  mellifica  Linn.  (Nos.  1237-1248).  The  larva 
(No.  1237)  is  a  soft  colorless  and  footless  grub.  While 
this  is  true  of  the  larva,  as  one  sees  it,  it  has  been  found 
that  legs  arise  very  early  in  larval  life  and  grow  in  the 
interior  of  the  body,  but  their  development  is  suppressed 
so  that  the  young  bee  has  no  functional  legs. 

The  mouth  parts  are  small  and  weak,  since  the  food  is 
of  a  pasty  nature  and  the  larva  is  supplied  with  it  by  cer- 
tain adults  specialized  for  the  purpose.  It  is  extremely 
nutritious,  consisting  of  pollen,  the  vitalizing  male  ele- 
ment of  plants,  and  of  honey,  the  nectar  of  flowers  that 


METAZOA INSECTA.  483 

has  undergone  a  chemical  change  in  the  honey  bags 
within  the  body  of  the  bee.  This  helplessness  of  the 
larva  is  in  striking  contrast  to  the  independence  of  the 
larvae  of  the  Lepidoptera  and  of  most  generalized  insects. 

The  larva  spins  a  thin  cocoon  for  the  protection  of  the 
pupa  (No.  1238).  The  appendages  of  the  pupa  are  nearly 
free,  although  each  one  is  covered  by  a  delicate  skin. 
The  metamorphosis  is  rapid,  twenty-four  days  being  re- 
quired for  the  male,  twenty-one  for  the  female,  and  only 
fifteen  or  sixteen  for  the  queen. 

The  body  of  the  adult  bee  (No.  1239;  PI.  1240;  fig. 
i,  c? ,  fig.  2,  9  ,  fig-  3,  ?  )  is  shortened,  compact,  and  hairy. 
The  three  regions  are  clearly  differentiated,  the  junction 
between  the  head  and  thorax  and  the  thorax  and  abdo- 
men being  a  marked  feature. 

The  thorax  is  complex  and  its  three  segments  are  closely 
consolidated  on  the  dorsal  side.  The  prothorax  (PI.  1241, 
fig-  J>  9  i/)  is  reduced  in  size.  Its  side  pieces  are  de- 
tached from  the  dorsal  portion  causing  the  fore  legs  to 
work  in  connection  with  the  head. 

The  mesothorax  (PI.  1241,  fig.  i,  ms]  forms  the  greater 
part  of  the  thorax,  while  the  metathorax  (fig.  i,  ;;//)  is 
narrow.  The  unique  character  of  the  Hymenoptera  is 
the  close  union  of  the  first  abdominal  segment  (fig.  i,  ab'\ 
usually  called  the  median  segment  or  propodeum,  with 
the  metathorax.  The  tendency  of  this  segment  to  press 
forward  is  seen  in  the  more  generalized  orders,  like  the 
Orthoptera  and  Hemiptera,  but  nowhere  is  it  carried  to 
such  an  extreme  as  in  the  Hymenoptera  and  Diptera. 

The  narrow  junction  of  the  thorax  with  the  abdomen  is 
effected  by  the  short,  slender  peduncle  (fig.  i,  ab"}  which 
is  in  reality  the  second  abdominal  segment,  although  usu- 
ally described  as  the  first. 

This  articulation  is  doubtless  produced  by  the  habit  of 
stinging,  and  it  is  an  extremely  perfect  mechanical  con- 
trivance. 

The    appendages   of   the    head  are  the  antennae  and 


484  SYNOPTIC  COLLECTION. 

mouth  parts,  as  in  most  insects,  but  the  antennae  differ 
from  those  of  other  orders  in  being  elbowed  and  bent 
upon  the  face.  The  mouth  parts  offer  one  of  the  best 
illustrations  of  specialization  by  addition.  Not  only  are 
these  strong,  chitinous  mandibles  (PL  1241,  fig.  i,  md) 
adapted  for  biting,  cutting,  kneading  wax,  crushing,  and 
chewing,  but  the  two  pairs  of  united  maxillae  (fig.  i,  mx\ 
mx")  are  fitted  for  piercing,  sucking,  and  lapping.  The 
ligula  (fig.  i,  mx",  /)  of  the  second  pair  of  maxillae  is  the 
part  usually  described  as  the  proboscis  and  its  length 
varies  in  different  species  of  bees  in  accordance  with  the 
varying  length  of  the  corollas  of  flowers  frequented  by 
these  insects. 

The  legs  are  long,  hairy  organs,  and  the  tibia  of  the 
third  pair  in  the  worker  bee  is  provided  with  little  cavities 
or  baskets  for  holding  pollen.  Thus  it  is  seen  that  the 
function  of  walking  is  combined  with  that  of  carrying 
food. 

The  tarsus  or  foot,  a  part  of  which  is  represented  in 
fig.  2,  side  view,  illustrates  the  correlation  of  structure 
and  habit.  By  means  of  the  hooks  the  bee  walks  on  the 
edges  of  its  comb,  and  hangs  from  other  bees,  while  the 
soft  cushion  or  pulvillus  seen  at  the  end  secretes  a  sticky 
substance  which  enables  the  insect  to  walk  on  the  polished 
surfaces  of  leaves  and  glass. 

The  wings  of  the  second  pair  are  reduced  in  size  like 
the  metathorax,  which  bears  them.  They  are  membra- 
nous—  hence  the  name  of  Hymenoptera,  meaning  mem- 
brane and  wing  —  and  have  few  veins.  The  two  pairs 
(PI.  1242,  figs,  i,  2)  are  fastened  together  by  hooks.  A 
portion  of  the  posterior  edge  of  the  fore  wing  turns  under 
in  a  plait  (fig.  i  ;  fig.  3,  the  plait  enlarged)  and  a  part  of 
the  anterior  edge  of  the  hind  wing  is  provided  with  hooks 
(fig.  2  ;  fig.  4,  hooks  enlarged)  ;  the  two  hook  together  as 
seen  in  fig.  5.  This  specialized  condition  enables  the 
two  wings  to  strike  the  air  as  one  organ  and  long  sus- 
tained flight  to  become  possible. 


METAZOA INSECTA.  485 

There  are  among  bees  no  wingless  forms,  and  this  is 
another  proof  that  these  insects  are  examples  of  special- 
ization by  addition. 

The  abdomen  bears  a  sting  which,  however,  is  within 
the  body.  The  origin  of  this  organ  is  similar  to  that  of 
the  ovipositor  of  locusts.  Connected  with  the  sting  are 
two  poison  glands.  The  abdomen  of  the  worker  is  pro- 
vided with  glands  for  secreting  wax.  These  are  on  the 
lower  side  and  the  wax  is  secreted  in  the  form  of  scales 
which  are  worked  over  by  the  bees. 

A  prosperous  colony  of  Apis  consists  of  from  80,000  to 
90,000  bees.  Of  these  a  few  hundred  are  males,  one  is  a 
female  or  queen,  and  the  remainder  are  workers.  Through 
the  partial  or  complete  suppression  of  the  genital  organs, 
and  also  through  the  acquisition  of  adaptive  features,  the 
workers  of  Apis  have  become  differentiated  to  a  greater 
degree  than  those  of  any  other  colony  of  bees.  They  se- 
crete the  wax  for  the  comb  (No.  1243),  the  hexagonal 
cells  of  which  are  cradles  for  the  young  and  storehouses 
for  honey.  They,  in  brief,  carry  on  all  the  industrial 
work  of  the  hive  and  are  equipped,  as  we  have  seen,  with 
pollen  baskets,  wax-secreting  glands  and  honey  bags,  none 
of  which  the  male  or  female  possesses. 

There  seems  to  be  a  superabundance  of  males,  many 
of  whom  do  little  or  nothing ;  a  few  only  of  the  number 
aid  in  perpetuating  the  race.  In  the  early  spring  the 
queen  begins  to  lay  eggs  and  is  capable  of  laying  4,000 
in  twenty-four  hours.  So  prolific  is  she  that  in  time  the 
nest  or  hive  becomes  overcrowded.  Then  it  is  that  the 
old  queen  with  from  60,000  to  70,000  workers  emigrates 
and  founds  a  new  home,  leaving  in  the  old  nest  some 
20,000  or  30,000  workers,  many  developing  larvae  and 
pupae  (from  one  of  which  the  new  queen  will  eventually 
be  born),  and  thousands  of  cells  filled  with  honey.  This 
is  called  the  primary  swarm ;  the  second  swarm,  that 
often  takes  place  later,  is  led  by  the  new  queen.  After 
this  second  swarm  has  settled  in  its  home,  the  new  queen 


486  SYNOPTIC    COLLECTION. 

with  many  males  takes  the  nuptial  flight,  after  which  egg- 
laying  begins  and  continues  for  several  seasons,  the  queen 
often  living  for  four  or  five  years. 

Formicidae.  Specialization  has  gone  on  in  ants  till 
there  are  no  solitary  forms,  all  the  species  living  together 
in  colonies.  There  are,  however,  simple  colonies,  like 
those  we  have  already  found  in  wasps  and  bees.  It  has 
been  observed  and  the  observation  proven  by  experiment 
that  a  colony  of  Camponotus  ligniperdus  is  started  by  a 
single  female  who  carries  on  the  industrial  work  of  the 
nest  until  her  worker-children  are  old  enough  to  assume 
the  burden. 

In  the  ant  the  body  is  less  consolidated  than  in  the 
bee,  but  Jn  this  case  this  lack  of  concentration  is  evidently 
a  specialized  condition  and  must  not  be  confused  with 
the  unconsolidated  state  of  primitive  forms.  That  this 
laxity  is  an  evidence  of  specialization  is  shown  by  the 
fact  that  there  is  less  concentration  in  the  specialized 
wingless  workers  than  in  the  winged  males  and  females. 
The  habits  of  these  insects  are  such  that  great  mobility 
of  body  is  necessary  and  therefore  lack  of  concentration 
has  become  a  secondary  and  adaptive  character.  The 
peculiar  junction  of  the  thorax  and  abdomen  has  prob- 
ably been  produced  by  the  habit  of  stinging.  The  pe- 
duncle is  formed  of  either  the  second  abdominal  segment 
or  the  second  and  third  segments  (counting  the  pro- 
podeum  attached  to  the  thorax  as  the  first).  These  seg- 
ments are  extremely  slender  and  are  called  nodes ;  by 
means  of  these  the  power  of  stinging  is  greatly  increased. 
It  is  noticeable  that  there  is  but  one  of  these  nodes  in 
most  of  the  stingless  species,  as  for  instance  in  Campo- 
notus. An  extreme  modification  of  the  abdomen  is  seen 
in  Cremastogaster  (PL  1244,  figs.  1,2)  where  this  part  of 
the  body  can  be  thrown  forward  over  the  thorax  and 
head. 

Specialization  among  the  ants  has  brought  about  divi- 
sion of  labor,  and  correlatively  the  peculiar  structures 


METAZOA INSECTA.  487 

which  fit  the  laborers  for  their  special  duties.  Not  only 
are  there  males  (PI.  1245,  fig.  i,  Formica  pennsylvanica 
De  Geer),  females  (fig.  2),  and  workers  (fig.  3),  as  in  the 
bee,  but  there  are  soldiers  (fig.  4)  and  the  workers  and 
soldiers  are  differentiated  still  further  so  that  other  forms 
appear,  each  one  with  its  particular  work  to  perform. 

The  males  and  females  are  provided  with  wings  until 
after  the  nuptial  flight,  when  the  males  are  killed  and  the 
female  sheds  these  organs.  The  workers,  however,  are 
always  wingless,  and  are  therefore  examples  of  specializa- 
tion by  reduction.  Even  the  sutures  between  the  seg- 
ments on  the  dorsal  side  are  often  obliterated,  while  they 
may  be  clearly  seen  in  the  winged  male  and  female. 

A  colony  of  ants  consists  of  males,  many  queens  instead 
of  one  as  in  the  bees,  and  thousands  of  workers  and  sol- 
diers. The  workers  do  all  the  industrial  work  of  the  nest, 
while  the  soldiers  with  their  great  heads  and  strong  man- 
dibles defend  the  colony.  The  winged  individuals  and 
the  workers  and  soldiers  of  some  species,  Atta  for  instance 
(No.  1246,  A.  fervens  Say,  $ ;  No.  1247,  the  same,  $)» 
are  differentiated  so  that  the  subject  of  polymorphism  is 
admirably  illustrated. 

The  organization  of  the  colony  continues  for  years  and 
the  mother  ant  lives  to  see  her  children  grow  to  maturity. 
It  seems  that  the  young  are  more  helpless  and  also  more 
tenderly  cared  for  than  in  any  other  group  of  insects. 
They  have  the  advantage  of  living  with  the  old  ants  and 
of  profiting  by  their  experience.  These  conditions  exist- 
ing for  unnumbered  years  and  countless  generations  have 
led  to  the  present  efficient  and  intelligent  social  order. 

Order  16. —  DIPTERA. 

The  Diptera  illustrate  pre-eminently  the  efficiency 
which  may  be  attained  through  specialization  by  reduc- 
tion. These  specializations  will  be  brought  out  more 
clearly  when  considering  a  typical  form  of  the  order, 


488  SYNOPTIC    COLLECTION. 

Tabanus  lineola  Fabr.,  but  first  the  characters  of  the  more 
generalized  Diptera,  the  Orthorhapha,  must  become  fa- 
miliar. 

The  Tipulidae,  represented  by  the  crane-flies,  have 
cylindrical,  colorless,  footless  larvae  (PI.  1248,  fig.  i,  Tip 
ula  eluta  Loew),  proving  that  even  in  these  most  general- 
ized members  of  the  order  the  Thysanuriform  larval 
stage  is  wholly  skipped.  The  larvae,  however,  have 
horny  mandibles  for  biting ;  they  also  have  tubercles  in 
place  of  feet. 

The  pupa  (fig.  2)  is  free;  that  is,  it  is  not  enclosed  in 
the  hardened  larval  skin,  the  puparium,  but  is  naked  and 
the  thoracic  appendages  are  clearly  seen.  In  this  stage 
the  respiratory  tubes  extend  from  the  prothorax. 

The  adult  Tipula  (No.  1249)  has  a  long  body  with 
the  thoracic  segments  extended  and  plainly  visible  (PI. 
1250,  fig.  i,  dorsal  view  of  thorax  of  Tipula;  fig.  2,  side 
view  of  same). 

The  feeble  legs  are  extremely  long.  The  wings  are 
reduced  to  one  pair,  the  second  pair  of  most  insects  act- 
ing as  balancers  or  poisers.  Proof  that  the  balancers 
were  originally  wings  is  found  in  the  fact  that  in  the 
pupal  stage  of  several  species  of  Diptera  these  organs 
are  large  and  broad. 

The  Tipulidae,  like  all  Diptera,  are  without  a  sting, 
and,  as  one  might  expect,  the  abdomen  is  not  peduncu- 
lated.  Tipula,  however,  like  the  more  generalized  insects, 
has  an  external  ovipositor  with  which  it  makes  holes  in 
earth,  fungi,  and  the  like  for  its  eggs. 

One  species  of  this  family,  Tipula  agarici  seticornis  De 
Geer,  according  to  De  Geer,  has  two  spinnerets  for  spin- 
ning silk.1 

The  Culicidae  or  mosquitoes  resemble  the  Tipulidae 
in  certain  adult  characters,  but  the  larvae  are  aquatic. 
The  eggs  (PL  1251,  fig.  i,  Culex  pungens  Wied)  are  laid 

iRirby  and  Spence,  Introd.  to  Ent,  III,  1826,  p.  125. 


METAZOA — INSECTA.  489 

in  masses  of  various  shapes  and  the  young  larvae  (fig.  2) 
are  extremely  active.  They  breathe  by  means  of  a 
respiratory  tube  which  extends  to  the  surface  of  the  water, 
as  seen  in  fig.  2.  According  to  Howard  the  organs  at 
the  end  of  the  abdomen  called  gill  flaps  (see  No.  1252, 
species  unknown)  may  be  respiratory  in  the  young  larva 
but  later  are  probably  locomotor  organs.  These  are 
seen  more  plainly  in  the  full  grown  larva  (PI.  1251,  fig.  3). 
The  development  is  accelerated  and  when  sevjen  days  have 
passed  the  larva  becomes  a  pupa  (fig.  4).  In  this  stage 
it  remains  quiet  at  the  surface  unless  disturbed  when  it 
moves  by  means  of  the  muscles  of  the  abdomen.  It  is  a 
most  peculiar  looking  insect  on  account  of  the  swollen 
thoracic  region.  It  breathes  now  by  means  of  two  tubes 
on  the  thorax  seen  in  No.  1252.  The  pupal  stage  is 
only  two  days  long  when  the  adults  (No.  1253  ;  PI.  1251, 
%  S»  6*;  ng.  6,  9)  emerge. 

The  genus  Anopheles  is  of  especial  interest  on  account 
of  the  part  it  plays  in  the  transmission  of  disease.  It 
has  been  discovered  that  the  malaria  germ  is  a  Protozoan 
which  lives  as  a  parasite  in  human  blood.  When  Ano- 
pheles maculipennis  bites  a  person  infected  by  this  para- 
site it  sucks  up  into  its  own  body  the  malarial  germ  which 
in  a  short  time  undergoes  a  true  sexual  development. 
The  fertilized  parasite  ultimately  passes  into  the  proboscis 
of  the  mosquito  and  is  injected  with  the  poison  into  the 
next  person  the  insect  bites,  who  thereby  becomes  a  vic- 
tim to  malaria.  While  the  larva  of  Culex  is  usually  seen 
in  the  position  represented  in  PL  1251,  fig.  2,  the  larva  of 
Anopheles  rests  in  a  nearly  horizontal  position  just  beneath 
the  surface  of  the  water.  The  head  of  the  latter  rotates 
and,  according  to  Howard,  can  be  turned  completely 
round  with  the  utmost  ease,  so  that  the  insect  has  the 
habit  of  lying  with  its  head  upside  down.  The  adults 
(No.  1254)  are  strong  and  bloodthirsty.  The  female 
Anopheles  can  be  distinguished  from  the  female  of  Culex 
by  its  long  palpi.  When  resting,  the  body  of  Anopheles 


490  SYNOPTIC    COLLECTION. 

is  straight ;  that  is,  the  head,  thorax,  and  abdomen  are  in 
a  horizontal  line,  while  the  body  of  Culex  is  hump- 
backed. 

Among  the  most  carnivorous  Diptera,  both  in  the  lar- 
val and  adult  stages,  is  the  robber-fly,  Asilus  sericeus  Say 
(No.  1255).  It  is  well  adapted  for  the  life  which  it  leads, 
by  having  a  robust  body,  bristling  with  stiff  hairs,  a 
strong,  black  proboscis  able  to  inflict  severe  wounds,  legs 
armed  with  spines  and  fitted  for  running,  seizing  prey, 
climbing,  and  digging,  and  wings  with  muscles  capable  of 
rapid  flight. 

Many  of  the  specializations  of  the  Diptera  are  well 
shown  in  the  type  form,  Tabanus.  The  larva  (PL  1256, 
fig.  i,  Tabanus  atratus  Fabr.)  tapers  at  both  ends  and  in 
this  way  differs  from  the  larvae  of  the  Tipulidae.  It  is  a 
footless  animal  with  a  head  provided  with  curved  dark 
brown  mandibles. 

The  pupae  (fig.  2,  Tabanus  lineola  Fabr.)  are  free  and 
may  be  distinguished  by  the  large,  ear-shaped  spiracles 
on  the  thorax.  In  the  Orthorhapha  the  winged  insect 
emerges  through  a  slit  on  the  back  of  the  pupa.  The 
short,  compact  body  of  the  adult  (No.  1257;  PL  1256, 
fig.  3  ;  No.  1258,  a  larger  species  of  Tabanus)  exhibits 
extreme  concentration  of  parts,  while  at  the  same  time 
the  three  regions  are  sharply  differentiated  from  one 
another. 

The  broad  head  with  its  great  compound  eyes  is  on  a 
pivot-like  neck.  The  thorax  is  complex  in  structure, 
differing  from  the  more  generalized  thorax  of  the  Tip- 
ulidae. The  reduced  collar-like  prothorax  (PL  1256,  fig. 
4,/)  is  firmly  soldered  to  the  large  mesothorax  (fig.  4, 
ms).  The  metathorax  (fig.  4,  mt)  is  only  partly  seen 
from  above,  the  basal  portion  of  the  abdomen  having 
crowded  forward  and  covered  up  its  posterior,  dark- 
colored  bulbous  portion  or  scutellum  (fig.  4,  scr").  This 
part  is  still  better  seen  in  fig.  5.  which  is  a  drawing  of 
the  head  and  thorax  seen  from  the  side.  This  peculiar 


METAZOA INSECTA.  491 

structure  gives  rise  apparently  to  a  sessile  abdomen,  but 
this  condition  must  not  be  confused  with  the  true  sessile 
abdomen  of  the  generalized  insects,  like  that  of  the 
Orthoptera  and  Hemiptera.  It  may  be  called  a  pseudo- 
sessile  abdomen  which  may  have  arisen  from  a  peduncu- 
lated  abdomen  by  the  reduction  of  the  peduncle  and  the 
complete  concealment  of  the  posterior  part  of  the  meta- 
thorax  by  the  basal  abdominal  segment. 

The  antennae  for  some  unknown  reason  have  the  third 
joint  enlarged.  The  mouth  parts  are  complex  organs 
and  are  fitted  for  piercing,  sucking,  and  lapping.  The 
mandibles  (fig.  4,  md)  and  the  first  pair  of  maxillae  (fig. 
4,  mx ')  with  their  large  palpi  are  modified  into  sharp 
piercing  organs.  The  second  pair  of  maxillae  (fig.  4, 
mx  ")  are  composed  of  leaf-like  parts  that  spread  out  and 
are  used  for  lapping  sweet  fluids. 

The  phylogenetic  studies  of  Kellogg L  have  thrown 
much  light  on  the  Dipterous  mouth  parts.  He  shows 
the  necessity  of  first  becoming  familiar  with  the  mouth 
organs  of  generalized  Diptera  in  order  to  interpret  rightly 
the  complex  structure  of  these  organs  in  specialized  forms 
such  as  the  Muscidae  (see  p.  493). 

The  legs  of  Tabanus  are  long  and  the  hairs  of  the 
cushions  of  the  feet  secrete  a  sticky  substance  which 
enables  the  fly  to  walk  on  a  ceiling.  The  process  of  spe- 
cialization by  reduction  has  reduced  the  number  of  wings 
from  four  to  two  ;  hence  the  name  of  Diptera,  meaning 
two  and  wing.  These  wings  are  strong  and  the  flight 
is  exceedingly  swift.  We  have  already  seen  that  a  pair 
of  balancers,  also  called  halteres  (fig.  4,  w")  represent  the 
second  pair  of  wings.  The  function  of  these  organs  is 
not  known  with  certainty.  They  may  be  sense  organs 
(Sharp)  assisting  in  the  perception  of  sound.  They  also 
seem  to  aid  in  preserving  the  equilibrium  of  the  body, 
and  they  may  be  useful  in  directing  the  flight  of  the 
insect. 

'Psyche,  VIII,  no.  273,   1899;     Biol.  Bull.,   I,  no.  2,  1900. 


492  SYNOPTIC    COLLECTION. 

The  Cecidomyidae  or  gall  gnats  are  among  the  more 
specialized  forms  of  the  Orthorhapha.  The  larva  of  one 
species  of  Cecidomyia  (C.  strobiloides)  makes  the  pine- 
cone  willow  gall  (No.  1259)  which  resembles  strikingly 
a  pine  cone.  The  gall  is  really  a  deformed  bud  produced 
by  the  larva  which  lives  within  the  gall  until  ready  to 
transform. 

The  Hessian  fly,  Cecidomyia  destructor  Say,  (PL  1260, 
figs.  1-4)  differs  from  Cecidomyia  strobiloides,  since  its 
larva  does  not  make  a  true  gall.  This  larva  (fig.  i)  has 
the  head  and  mouth  parts  in  such  a  vestigial  condition 
that  it  absorbs  its  food,  which  is  the  sap  of  the  wheat. 
When  ready  to  transform,  its  skin  becomes  hard,  brown, 
and  unsegmented.  The  pupa  (fig.  2,  ventral  view) 
within  this  hardened  case  or  puparium  (fig.  3)  remains 
absolutely  motionless.  On  account  of  the  resemblance 
of  the  puparium  to  a  flax  seed  this  is  known  as  the 
"flax  seed  state"  of  the  insect.  The  presence  of  these 
"flaxseeds"  between  the  leaf  and  the  stalk  of  the  wheat 
causes  the  stem  to  swell  and  the  leaves  to  die  (Packard) 
and  thus  in  both  the  larval  and  the  pupal  stage  the  insect 
does  great  damage  to  the  wheat  crop. 

It  is  interesting  to  note  that  in  this  Dipterous  family, 
the  Cecidomyidae,  there  :,  an  extremely  interesting  form, 
Miastor,  whose  larvae  are  capable  of  laying  eggs.  Here 
is  a  case  where  it  would  seem  that  the  law  of  acceleration 
in  development  has  acted  so  that  the  egg-laying  habit 
peculiar  to  the  adult  stage  in  most  animals  has  been  car- 
ried back  to  the  larval  stage. 

The  next  division  of  flies,  the  Cyclorhapha,  are  more 
specialized  than  the  Orthorhapha,  both  in  the  larval  and 
adult  condition.  The  group  is  represented  by  the  flesh- 
fly.  Sarcophaga  (No.  1261);  and  the  house-fly,  Musca 
domestica  Linn.  (No.  1262).  The  larva  or  "maggot"  of 
Musca  is  more  reduced  than  that  of  Tabanus.  The  head 
has  nearly  disappeared,  and  the  mouth  parts  exist  as  mere 
vestiges. 


METAZOA INSECTA.  493 

In  the  transformation  from  larva  to  pupa  most  of  the 
larval  organs  are  destroyed,  while  from  the  so  called  "im- 
aginal  buds"  that  persist  the  parts  of  the  pupa  and  imago 
arise.  The  pupa  transforms  in  a  puparium,  and  emerges 
in  this  entire  group  (Cyclorhapha)  through  an  opening  at 
the  anterior  end  which  is  provided  with  a  lid.  The  de- 
velopment is  accelerated  requiring  from  ten  to  fourteen 
days  only,  and  according  to  Weismann  this  metamorphosis 
of  the  Muscidae  is  far  more  complex  than  in  other  insects. 

The  adult  Musca  (No.  1262)  is  also  more  reduced  than 
the  adult  Tabanus.  The  mandibles  and  first  pair  of 
maxillae  have  become  useless  and  the  mouth  parts  have 
only  one  function, —  that  of  lapping.  That  this  function 
is  performed  with  admirable  perfection  is  demonstrated 
whenever  Musca  is  watched  sipping  its  meal  of  sweetened 
water. 

The  parasitic  Diptera  —  the  Pupipara  —  are  reduced  to 
the  extremest  degree.  The  wings  have  not  only  become 
tiny  scales  as  in  the  semi-parasitic  flea,  Pulex,  but  in  the 
Pupipara  both  wings  and  balancers  are  wanting  altogether, 
as  seen  in  Melophagus  ovinus  Linn.  (PI.  1263,  fig.  i)  and 
Braula  coeca  Nitzsch  (fig.  2).  With  this  reduction  of  the 
wings  the  thoracic  segments  have  lost  their  typical  fea- 
tures and  in  Braula  have  becd^ne  like  those  of  the  abdo- 
men (see  fig.  2).  But  this  is  not  all.  The  remarkable 
discovery  by  Adensamer  of  the  bee  parasite,  Ascodipteron 
(PL  1264,  A.phyllorhinae,  dorsal  view),  proves  that  among 
insects  the  law  of  specialization  by  reduction  may  obliter- 
ate all  trace  of  segmentation.  In  this  parasite  there  is  no 
external  head  and  only  the  structure  of  the  internal  organs 
places  it  near  Melophagus. 

The  Pupipara  develop  by  a  process  that  is  remotely 
comparable  to  that  of  vertebrates.  The  young  are  re- 
tained in  an  enlargement  of  the  oviduct  and  are  nourished 
by  a  milk-like  secretion.  The  larval  stage  is  nearly  or 
wholly  passed  within  the  body  of  the  parent  so  that  the 
young  are  born  as  pupae  —  a  unique  illustration  of  the 
law  of  acceleration  in  development. 


494  SYNOPTIC    COLLECTION. 

The  great  class  of  Insecta  may  be  considered  as  the 
most  specialized  of  invertebrates.  We  have  briefly  traced 
the  evolution  of  this  class  from  the  ancestral  type  as 
expressed  by  the  Thysanura  to  the  extremely  differen- 
tiated forms  of  the  Hymenoptera  and  Diptera.  The 
primitive  development  of  the  simplest,  wingless  species 
and  the  straightforward,  direct  development  of  the  more 
generalized  winged  forms  are  seen  to  be  processes  which, 
if  understood,  throw  strong  light  on  those  complex  meta- 
morphoses that  characterize  the  method  of  indirect  devel- 
opment, and  that  make  the  study  of  insects  at  once  most 
attractive  and  most  difficult. 

In  no  class  of  invertebrates  are  there  such  varied 
adaptations  of  structure  to  the  favorable  and  adverse 
conditions  of  environment  with  the  correlative  increase 
or  decrease  in  organs  as  in  the  Insecta.  The  Hymenop- 
tera and  Diptera  challenge  each  other  as  demonstrators 
of  the  law  of  specialization, —  the  one  of  specialization 
by  addition  and  the  other  of  specialization  by  reduction. 
These  forces  we  have  found  operative  in  most  of  the 
subkingdoms  of  invertebrates,  but  nowhere  to  such  an 
extreme  degree  as  in  these  two  remarkable  and  intensely 
interesting  orders  of  insects  —  the  intelligent,  progressive 
Hymenoptera,  and  the  adaptive,  reduced  Diptera. 


ALPHABETICAL    LIST   OF   GENERA   MENTIONED    IN 
THIS   GUIDE. 


(Synonyms   are   in    italics.) 


Abyla,  in. 
Acanthia,  423. 
Acanthosphoera,  41. 
Acaulis,  99,  100. 
Acervularia,  135. 
Achorutes,  395. 
Acmaea,  215. 
Acronycta,  463. 
Acrosoma,  369,  373. 
Actias,  468. 
Actinocrinus,  156, 157. 
Actinometra,  160. 
Actinophrys,  39,41. 
Actinosphaerium,  39. 
Actissa,  41-44. 
Adamsia,  130. 
Adeona,  288. 
Adeonellopsis,  288. 
Adranes,  435. 
Aeginopsis,  96,  98,  105. 
Aeolis,  234. 
Aeschna,  401. 
Agalena,  369,370. 
Agalma,  1 10. 
Agaricia,  138. 
Ag°lacrinus,  161. 
Aglaophenia,  92. 
Aglaura,  98,  99. 
Agrion,  401. 
Alaurina,  319. 
Alaus,  440. 
Alcvonium,  119. 
Alp'heus,  343. 
Ammolynthus,  85. 
Ammonites,  253. 
Ammonites,  252,  253. 
Ammosolenia,  85. 


Ammothea,  120. 
Amoeba,  21-28,  31,  46. 
Amphidetus,  189. 
Amphitrite,  300. 
Amphizoa,  434. 
Ampularia,  230. 
Amygdalocystis,  147. 
Anabolia,  451. 
Anasa,  420,  422. 
Anatina,  198,  199. 
Ancylus,  230. 
Anemonia,  130. 
A  ngiosto m urn,  313. 
Anisopteryx,  462. 
Anodonta,  209,  210. 
Anomia,  205. 
Anopheles,  489. 
Antedon,  158-160. 
Anthea,  130. 
Anthelia,  118. 
Anthonomus,  445. 
Anthophora,  442. 
Anthrenus,  439. 
Antillia,  136,  137. 
Antipathes,  126,  127. 
Anurida,  390 
Aphrodite,  294. 
Aphis,  426. 
Apiocrinus,  157. 
Apis,  482,  485. 
Aplvsia,  232,  233. 
Aplysilla,  86. 
Apolemia,  in. 
Apus,  329,  330. 
Arbacia,  179. 
Area,  202. 
Archerina,  14,  17. 


496 


SYNOPTIC    COLLECTION. 


Arenicola,  299,  300. 
Argiope,  369,  372. 
Argonauta,  261. 
Arietites,  253. 
Aristocystis,  146. 
Artemia,  328,  329. 
Arthrolycosa,  368. 
Ascalaphus,  448. 
Ascaris,  313. 
Ascetta,  65,  69,  70,  72. 
Ascodipteron,  493. 
Asellus,  339. 
Asilus,  490. 
Aspergillum,  201. 
Aspidisca,  460. 
Asterias,  165-170. 
Asteroceras,  253. 
Astrangia,  137. 
Astroides,  140. 
Astropecten,  163. 
Astrophyton,  170,  171, 
Astrorhiza,  31,  32. 
Astyris,  223. 
Atax,  3.74. 
Atlanta,  237. 
Atropos,  409. 
Atrypa,  284,  285. 
Atta,  487. 
Attagenus,  440. 
Attus,  373. 
Aturia,  254. 
Audouinia,  300. 
Aulacoceras,  257. 
Aulactinia,  128. 
Aulica,  225. 
Aulopora,  114,  115. 
Aurelia.  105-  108. 
Autolytus,  296,  297. 
AviciTla,  206. 
Aviculopecten,  203. 
Aviculopinna,  206. 

Bactrites,  250. 
Baculites,  256,  257 
Balaninus,  446. 
Balantium,  242. 
Balanus,  332,  333. 


Barrettia,  134. 

Bathybius,  15,  16,  31. 

Belemnites,  257,  258. 

Belosepia,  258. 

Belostoma,  419-421. 

Benacus,  419. 

Beroe,  112. 

Bicidium,  131. 

Biflustra,  288. 

Bilobites,  275. 

Biloculina,  33. 

Birgus,  353. 

Bittacus,  450. 

Blabera,  414. 

Blatta,  414. 

Bolina,  112. 

Bombus,  482. 

Bombyx,  466. 

Boophilus,  375. 

Boreus,  451. 

Borlasia,  316,  317. 

Bothriocephalus,  299. 

Bothriocidaris,    171,    172,    177 

178. 

Bouchardia,  283. 
Branch iomma,  302. 
Branchipus,  328,  329. 
Brancoceras,  251. 
Braula,  493. 
Briareum,  125. 
Buccinum,  222. 
Bugula,  288. 
Bullus,  232. 
Bunodes,  130. 

Cacoecia,  460. 
Caenis,  400. 
Calanus,  326. 
Calappa,  356. 
Calceola,  134. 
Calepteryx,  400. 
Callianassa,  349. 
Callinectes,  355. 
Callosamia,  468. 
Calopteryx,  400. 
Calosoma,  433- 
Calymene,  364. 


INDEX. 


497 


Cambarus,  347,  348. 
Campeloma,  231. 
Campodea,  389,  391-394. 
Campbnotus,  486. 
Cancer,  353. 
Cancrisocia,  358. 
Caprella,  338. 
Cardiola,  198. 
Cardiosoma,  356. 
Cardium,  212. 
Carinaria,  237. 
Carmarina,  98. 
Carteriospongia,  87. 
Carvocrinus,  148,  149. 
Caryophyllia,  136. 
Cassis,  226. 
Catenicella,  288. 
Caudina,  193. 
Cecidomvia,  492. 
Cellularia,  288. 
Cenia,  236. 
Cenosphoera,  40. 
Centronella,  277. 
Ceratiocaris,  334. 
Ceratites,  252. 
Ceratium,  51. 
Cerebratulus,  316,  317. 
Cerianthus,  126. 
Cerithium,  224. 
Cerura,  467. 
Cestum,  112. 
Ce/oc/tilus,  326. 
Cetonia,  314. 
Chaetopterus,  300. 
Chalcophora,  443. 
Chalinula,  81,  82. 
Chama,  213. 
Cheirocrinus,  it>8. 
Chirodota,  193. 
Chiton,  214. 
Chloeon,  397~399- 
Chondracanthus,  327. 
Chonetes,  274. 
Chrysopa,  447,  448. 
Cicada,  424,  426. 
Cicindela,  433. 
Cidaris,  173,  178. 


Cimbex,  476. 
Cionus,  446. 
Cistelia,  281-284. 
Cistenides,  301. 
Cladochonus,  1 14. 
Cladocora,  137. 
Cladognathus,  438. 
Cladonema.  101. 
Clathrulina,  17,  39,  40. 
Clava,  101. 
Clavularia,  118. 
Cleodora,  242. 
Clepsine,  308,  309. 
Clio,  242. 
Cliona,  79,  80. 
Clionc,  242. 
Clionopsis,  243. 
Clisiocampa,  468. 
Clubione,  367. 
Clypeaster,  183. 
Coccinella,  433. 
Codaster,  149.  150. 
Codosiga,  49. 
Coenopsammia.  140. 
Collozoum,  42. 
Collyrites,  188. 
Colobocentrotus,  180. 
Comatula,  159. 
Conchoderma,  333. 
Conocephalus,  417. 
Conularia,  239. 
Conns,  225. 
Coptodisca,  460,  461. 
Coralliochama,  213. 
Corallinm,  125. 
Corixa,  420. 
Cornularia,  117. 
Cornuspira.  32. 
Coronula,  333. 
Corydalns,  446,  447. 
Corvmorpha,  ICXD. 
Corynoides,  90. 
Corvstes,  356. 
Corvthuca,  423. 
Coscinoptera,  438. 
Cossus,  458. 
Cotalpa,  436. 


498 


SYNOPTIC    COLLECTION. 


Crangon,  343,  344. 
Crania,  271. 
Cremastogaster,  486. 
Crepidula,  218. 
Creseis,  240,  241. 
Crioceras,  255. 
Cristatella,  288. 
Crucibulum,  217. 
Cryptopodia,  359. 
Ctenaria,  in. 
Cteniza,  368,  370. 
Ctenodiscus,  162. 
Ctenoscolex,  289. 
Cucumaria,  192. 
Culex,  488-490. 
Cunina,  97,  98. 
Cunocantha,  97. 
Cunoctantha,  97. 
Cupressocrinus,  151,  153. 
Cuvieria,  241. 
Cyamus,  339. 
Cyanea,  105-107,  113,  131. 
Cyaniris,  470. 
Cyathaxonia,  135. 
Cyathocrinus,  151,  154,  155. 
Cyclolites,  139. 
Cyclops,  313,  327. 
Cyclostoma,  222,  230. 
Cymbium,  225-227. 
Cvmbulia,  241. 
Cynips,  477. 
Cypraea,  225,  227,  228. 
Cyprina,  212. 
Cyrtoceras,  246. 
Cyrtocerina,  245. 
Cyrtodaria,  200. 
Cyrtophyllus,  417. 
Cystiphyllum,  133. 
Cythere'a,  212. 
Cythocrania,  415. 

Dactylioceras,  253. 
Dalmanites,  364. 
Danais,  471-474. 
Darwinella,  85,  86. 
Dendronotus,  235. 
Dendrophyllia,  140. 


Dentalina,  35. 
Dentalium,  236. 
Deroceras,  252. 
Desmarella,  49,  50. 
Diadema,  179. 
Diapheromera,  415. 
Dictyophorus,  416. 
Dielasma,  278. 
Difflugia,  28-31. 
Dimorpha,  18,  28,  46,  47. 
Dinophilus,  290,  291. 
Diphragmoceras,  244,245,  247, 
Diplograptus,  91,  92. 
Diploria,  138. 
Discina,  271. 
Discinisca,  270. 
Dissosteira,  416. 
Distichopora,  95. 
Distomum,  321,  322. 
Donax,  212. 
Dorippe,  358. 
Doris,  236. 
Doryphora,  438. 
Dromia,  351. 
Dynastes,  438. 
Dytiscus,  434,  437. 

Echinanthus,  184. 
Echinarachnius,  184. 
Echinometra,  186. 
Echinoneus,  187. 
Echinorhynchus,  314. 
Eehinosphaerites,  148. 
Echinothrix,   180. 
Echinus,  182. 
Echiurus,  309. 
Edwardsia,  126. 
Elaphidion,  443. 
Eledone,  261. 
Eleodes,  440. 
Eleutherocrinus,  151. 
Elpidia,  190. 
Elysia,  236. 
Emesa,  423. 
Emphytus,  475,  476. 
Encope,  186. 
Encrinus,  151,  155. 


INDEX. 


499 


Endoceras,  244. 
Enoicyla,  454. 
Ensis,  211. 
Entimus,  446. 
Eolis,  234. 
Epargyreus,  468. 
Epeira,  369-371. 
Epeira,  372. 
Epicaerus,  445. 
Epicauta,  441. 
Epipyrops,  465. 
Erebus,  463. 
Eriocephala,  455,  456. 
Eriphia,  356. 
Estheria,  330. 
Eteone,  298. 
Eucalyptocrinus,  157. 
Eucyrtidium,  42. 
Euriicites,  289,  290. 
Eupagurus,  349,  350. 
Euphyllia,  138. 
Euplectella,  76. 
Eurypelma,  368. 
Eurystomites,  255. 
Eutermes,  408. 
Evatya,  343 

Fabricia,  305. 
Fasciolaria,  223. 
Favia,  138. 
Favosites,  116. 
Feniseca,  470. 
Filaria,  313. 
Filogrina,  288. 
Fissurella,  215-217. 
Flabellina,  235. 
Forficula,  411,  412. 
Formica,  487. 
Fulgora,  426. 
Fulgur,  223. 
Fungia,  139,  140. 
Fusilina,  38. 

Galathea,  348,  349. 
Galaxea,  138. 
Galerucella,  438. 
Galgulus,  422. 


Gammarus,  338. 
Gelasimus,  359. 
Geodia,  78. 
Gerris,  419. 
Geryonia,  98. 
Glaucus,  235. 
Globigerina,  35-38. 
Glottidia,  267,  269,  280. 
Glyptosphaera,  148. 
Goniatites,  251. 
Goniocidaris,  172,  173,  178. 
Gonionemus,  104,  105. 
Gonoplax,  360. 
Gonothyraea,  104,  105. 
Gordius,  312,  313. 
Grapsus,  357. 
Gryllotalpa,  417. 
Gryllus,  417. 
Gryphaea,  207. 
Gundlachia,  230. 
Gwynia,  283,  284. 
Gyrineum,  224. 
Gyrinus,  434. 
Gyroceras,  246. 
Gyrodactylus,  322. 

Haeckelina,  17,  32. 
Haemadipsa,  307,  308. 
Haematopinus,  424. 
Haimea,  1 16. 
Halcampa,  127. 
Haliclystus,  108. 
Haliotis,  215,  217. 
Haliphysema,  68. 
Halisarca,  67,  74,  75. 
Halla,  298,  299. 
Haltica,  439. 
Haplocrinus,  151-154. 
Hartea,  116,  117. 
Hastigerina,  38. 
Helcioniscus,  215,  216. 
Helicoceras,  255. 
Heliconius,  474. 
Helicopsyche,  453. 
Helicostyla,  231. 
Heliophyllum,  135. 
Heliothrips,  419. 


500 


SYNOPTIC    COLLECTION. 


Helix,  231,  232. 
Hemiaster,  188. 
Hemimerus,  412. 
Hemithyris,  277. 
Heodes,  470. 
Hepialus,  456. 
Hetaerina,  400. 
Heterocampa,  466. 
Heterocentrotus,  180. 
Hexagenia,  398. 
Hippa,  350,  351. 
Hippasteria,  163. 
Hippurites,  134. 
Hircinia,  86. 
Hirudo,  307-309. 
Holaster,  188. 
Holothuria,  192. 
Homaloneura,  397. 
Homarus,  344,  345. 
Hornia,  442. 
Hotinus,  426,  465. 
Hyalea,  241,  242. 
Hyalonema,  76. 
Hyas,  359. 
Hyboclypus,  187. 
Hydra,  102-104. 
Hydropsyche,  453. 
Hygrotrechus,  422. 
Hyolithes,  239. 
Hysteroconcha,  213. 

lanthina,  222. 
Icerya,  431. 
Ichneumon,  478. 
Idotea,  339. 
Idyia,  112,  1  13. 
Iphidea,  265,  266. 
Isis,  125. 
Isogenus,  405. 
Isotelus,  364. 
Ixa,  359. 


393. 
Julus,  383,  384. 

Kophobelemnon,  120. 
Kutorgina,  272. 


Lacazella,  273. 
Lachnosterna,  436. 
Laganum,  184. 
Lagena,  35. 
Lambrus,  359. 
Lampsilis,  209,  210. 
Lampyris,  436. 
Lepas,  332. 
Lepisma,  393,  394. 
Lepralia,  288. 
Leptaena,  273. 
Leptocerus,  453. 
Leptodesma,  206. 
Leptogorgia,  124. 
Leptoplana,  320 
Lernea,  327,  328. 
Leucania,  462. 
Leuconia,  73. 
Leucosolenia,  70,  85. 
Lib  ell  ula,  401. 
Libythea,  474. 
Lichas,  363. 
Lichenocrinus,  147. 
Limapontia,  236. 
Limax,  232. 
Limnaeus,  230,  321. 
Limnephilus,  453. 
Limothrips,  418.  419. 
Limulus,  326,  364-367 
Linckia,  164. 
Lineus,  315. 
Linguatula.  377,  378. 
Lingula,  267-269. 
Lingulepis,  267. 
Lipeurus,  409,  410. 
Lipura,  395. 
Lithodes.  352,  353. 
Lithophyllia,  136. 
Lithostrotion,  136. 
Litorina,  222. 
Lobiger,  233. 
Loligo,  260. 
Loligopsis,  251. 
Lophothuria,  192. 
Loxosoma,  287- 
Lucernaria,  108. 
Lucifer,  341. 


INDEX. 


501 


Ludius,  440. 
Lumbricus,  305. 
Lunatia,  218,  220,  221. 
Lycosa,  373,  374,  449. 
Lygia,  340. 
Lysiosquilla,  336. 
Lytoceras,  253. 

Macrobdella,  307. 

Macrosila,  465. 

Mactra,  211. 

Madrepora,    132    [not    Madre- 

poria],  141. 
Magas,  283,  284. 
Magasella,  283,  284. 
Magellania,  283,  284. 
Magilus,  223. 
Mahadeva,  369,  373. 
Maia,  359. 
Malleus,  206,  207. 
Mammillifera,  127. 
Manayunkia,  305. 
Manicina,  137,  138. 
Mantispa,  449. 
Marsupiocrinus,  157. 
Marsupites,  151,  156. 
Meckelia,  316,  317. 
Megalopyge,  457. 
Megerlina,  283. 
Melania,  231. 
Melanoplus,  416,  441. 
Melibe,  235. 
Melina,  206. 
Melitodes,  125. 
Melittia,  454.  461. 
Meloe,  442. 
Melonites,  175-178. 
Melophagus.  411,  493. 
Menopon,  410. 
Meoma,  189. 
Meristina,  286. 
Mesites,  147. 
Mesocystis,  147,  149. 
Mesopsocus,  409. 
Metacrinus,  158. 
Metalia,  189. 
Metoporhapis,  358. 


Metridium,  128. 
Miastor,  492. 
Michelinia,  115,  116. 
Micraster,  188. 
Microhydra,  101,  102. 
Miliola,"  33,  34. 
Millepora,  93-95. 
Millericrinus,  157. 
Mimoceras,  251. 
Modioloides,  198. 
Moira,  189. 
Monas,  47,  48,  53. 
Monograptus,  91. 
Monosiga,  48. 
Monoxenia.  116,  117. 
Morpho,  475. 
Murex,  225. 
Musca,  492,  493. 
Mussa,  137. 
Mutilla,  480. 
Mya,  200. 
My  gale,  368. 
Myrmeleon,  448. 
Myxodictyum,  16. 

Natica,  221. 
Nautilus,  246-249,  255. 
Neanura,  392. 
Nebalia,  334,  335. 
Necrophorus,  434,  435, 
Nemertes,  316. 
Nemognatha,  442. 
Nemoptera.  449. 
Neinoura,  404. 
Nepa,  419. 
Nephelis,  307. 
Nephila,  369,  370. 
Nephrops,  347. 
Nereis,  295,  296,  306. 
Nereites,  289. 
Nerice,  466. 
Nerita,  228,  229. 
Neritina,  228,  229. 
Neuronia,  452. 
Neverita,  221. 
Nirmus,  410. 
Noctiluca,  50-52. 


502 


SYNOPTIC    COLLECTION. 


Nodosaria,  35. 
Notonecta,  420. 
Nucleocrinus,  151. 
Nucula,  202,  206. 
Nummulites,  38. 
Nymphon,  376,  377. 

Obelia,  104,  105. 

Obolella,  266-268. 

Ocneria,  463. 

Octopus,  260,  261. 

Oculina,  136. 

Odynerus,  480. 

Oligoporus,  174,  175,  177,  178. 

Oligotoma,  408. 

Oliva,  225,  227. 

Ophiocoma,  170. 

Ophiopholis,  169. 

Ophioplocus,  170. 

Ophiura,  170. 

Orbicella,  138. 

Orbiculina,  34. 

Orbiculoidea,  271. 

Orbitolites,  34. 

Orbulina,  35-38. 

Orchelimum,  417,  480. 

Orchesella,  392. 

Orectochilus,  434. 

Orneodes,  459. 

Orophocrinus,  150. 

Orthis,  274. 

Orthoceras,  245,  248,  250. 

Ortkoceras,  241;. 

Orthosoma,  443. 

Orygoceras,  238,  239. 

Oscarella,  66,  67,  74. 

Ostrea,  206,  207. 

Ovulina,  30. 

Pachymyxa,  20. 
Pachyseris,  138. 
Pagurus,  130. 
Palaeaster,  163. 

Palaeechinus,     174,     175,    177, 

178. 

Palaemon,  342. 
Palaeocampa,  383-385. 


Palaeocaris,  333,  334. 
Palaeocyclus,  139. 
Palaeophlebia,  400. 
Paleacrita,  462. 
Palinurus,  345. 
Paludina^  231. 
Panorpa,  449,  450. 
Papilio,  469. 
Papirius,  394. 
Paralcyonium,  119. 
Paramoecium,  23,  53-55, 
Paraponyx,  459. 
Parthenothrips,  418. 
Patella,  215. 
Paterina,  265,  267. 
Paterula,  270. 
Patrobus,  433. 
Paulia,  164. 
Pecten,  203-205,  332. 
Pectinaria,  301. 
Pedicellina,  287. 
Pediculus,  424. 
Pelagia,  108. 
Pelomyxa,  27,  28. 
Pelta,  236. 
Penaeus,  341,  342. 
Penella,  327,  328. 
Peneroplis,  33,  34. 
Pennatula,  120. 
Pentaceros,  164. 
Pentacrinus,  158,  159. 
Pentacta,  192. 
Pentarnerus,  275. 
Pentremites,  150. 
Pepsis,  479. 
Pericera,  358. 
Peridinium.  50,  51. 
Peripatus,  378-382. 
Periplaneta,  414. 
Perisphinctes,  254. 
Perla,  404. 
Petricola,  210. 
Petrochirus,  350. 
Phalium,  226. 
Phascolosoma,  310. 
Phidippus,  373. 
Phlegethontius,  465. 


INDEX. 


503 


Pholas,  201. 
Phorodon,  426,427. 
Photuris,  435. 
Phoxichilidium,  376,  377. 
Phyllactis,  131. 
Phyllium,  415. 
Phyllobranchus,  236. 
Phylloceras,  254. 
Phyllocnistis,  461. 
Phjllodoce,  294. 
Phylloxera,  428,  430. 
Phjmactis,  131. 
Physalia,  no. 
Phytoptus,  376. 
Pieris,  469,  471. 
Pilidium,  315. 
Piloceras,  244. 
Pinna,  206. 
Planaria,  320. 
Planolites,  289. 
Planorbis,  231. 
Platephemera,  396. 
Plathemis,  401,  402,  404. 
Plat  veer  as,  215. 
Platycrinus,  156. 
Platypus,  444. 
Platystrophia,  274. 
Pleurobrachia,  in,  112. 
Pleurobranchus,  232,  233. 
Pleuroceras,  252. 
Pleurodictyum,  115,  116. 
Pleurophyllidia,  236. 
Pleurotomaria,  214,  215. 
Plexaura,  125. 
Plocamophorus,  236. 
Pneumodermon,  242. 
Pocillopora,  136. 
Podocoryne,  100. 
Podophrya,  59,  60. 
Polinices,  221. 
Polistes,  481. 
Polycirrus,  299. 
Polvgordius,  292. 
Polygyratia,  231. 
Pontobdella,  309. 
Pontolimax,  236. 
Porcellana,  352. 


Porites,  141. 
Porpita,  109. 
Porthetria,  463. 
Poteriocrinus,  155. 
Prionidus,  423. 
Productus,  274. 
Progonoblattina,  413. 
Prophysema,  68. 
Prosopis,  482. 
Prosopistoma,  399. 
Protamoeba,  13-15,  24,  53. 
Proterospongia,  50,  65,  66. 
Protogenes,  16. 
Protohydra,  102,  103. 
Protomyxa,  18-20. 
Protorhyncha,  276. 
Psammobia,  211. 
Psainmolyce,  295. 
Psammosolen,  211. 
Pseudothelphusa,  357. 
Psocus,  409. 
Psolus,  192. 
Psyche,  457. 
Pteria,  206. 
Pterinopecten,  203. 
Pteroceras,  226. 
Pteronarcys,  404. 
Pterotrachea,  238. 
Pterygotus,  366 
Pulex,  493. 

Pycnogonum;  376,  377. 
Pygaster,  182. 
Pyrgia,  114. 
Pyrina,  187. 
Pyrophorus,  440. 
Pyrrhactia,  464. 

Radiolites,  134,  213. 
Ranatra,  419,  421. 
Raninoides,  351. 
Raphiophora,  79. 
Reniera,  81. 
Renilla,  120-125. 
Reophax,  32 
Retepora,  288. 
Rhipidogorgia,  126. 
Rhizostoma,  108. 


504 


SYNOPTIC    COLLECTION. 


Rhodactis,  281. 
Rhoechinus,  174,  177,  178. 
Rhombopteria,  203,  206. 
Rhynchobolus,  298. 
Rhynchonella,  277,  280. 
Rotalina,  30. 

Sabella,  302. 
Saccammina,  31. 
Samia,  468. 
Sao,  361. 
Saperda,  443. 
Sarcophaga,  492. 
Sarcoptes,  375. 
Scala,  219. 
Scaphites,  255. 
Schizoneura,  430. 
Scolopendra,  385. 
Scolopendrella,  386,  387,  392 
Scotophanes,  190. 
Scutellera,  423. 
Scyllaea,  235. 
Scymnus,  433. 
Sepia,  258,  259. 
Seriatopora,  136. 
Serolis,  340. 
Serpula,  81,  303. 
Sertularia,  92. 
Sesia,  462. 
Setodes,  453. 
Sigalion,  294. 
Simnia,  228. 
Sipunculus,  310,  311. 
Solarium,  220. 
Solaster,  164. 
Solenomya,  198,  199. 
Spathegaster,  477. 
Sphaeroceras,  255. 
Sphaerogyna,  376. 
Sphex,  480. 
Spinosella,  84. 
Spirialis,  240. 
Spirifer,  285,  286. 
Spirographis,  302. 
Spirorbis,  303,  304. 
Spirula,  258. 
Spisttla,  211. 


Spongia,  87. 
Spongicola,  76.     • 
Spongilla,  80,  81. 
Spongodes,  120. 
Spurilla,  235. 
Spyroceras,  245. 
Squilla,  335-337. 
Stagmomantis,  415. 
Staphylinus,  436. 
Staurosphoera,  41. 
Stentor,  55,  56. 
Stephanoceras,  253. 
Stomatella,  217. 
Stringocephalus,  278. 
Strombus,  226. 
Strongylocentrotus,  181. 
Stylarioides,  301. 
Stylocordyla,  79,  80. 
Stylops,  442. 
Suberites,  78. 
Surcula,  220. 
Sycandra,  66,  71,  72. 
Sycon,  71. 
Synageles,  374. 
Synapta,  193. 
Syringopora,  119. 

Tabanus,  488,  490,  491. 
Taenia,  323,  324. 
Tealia,  130. 
Tectns.  225. 
Telea,  467.' 
Tenebrio,  440. 
Tentaculites,  238,  239. 
Terebella,  300,  301,  305. 
Terebra,  224. 
Terebratella,  283,  284. 
Terebratula,  278,  279. 
Terebratulina,  278-280. 
Teredo,  201. 
Termes,  405-407. 
Tessaradoma,  288. 
Tethya,  77,  78. 
Tethys,  235. 
Tetil'la,  77. 
Tetranychus,  374. 
Tettix,  417. 


INDEX. 


505 


Thalassicolla,  42. 
Thalassophysa,  42. 
Thalessa,  478. 
Thaumatocrinus,  158. 
Thecidium,  272-274. 
Thecla,  470. 
Theopilium,  42. 
T/irips,  418,  419. 
Thyridopteryx,  457. 
Thysanozoon,  319. 
Tibicen,  424. 
Tiedemannia,  241. 
Tima,  104,  105. 
Tinea,  460. 
Tipula,  488. 
Tornatella,  232. 
Tortrix,  460. 
Toxaster,  188. 
Tragos,  77. 
Tremex,  476,  478. 
Trevelyana,  236. 
Triarthrus,  362,  363. 
Tricoelocrinus,  151. 
Tricoma,  311. 
Tridacna,  213. 
Trigonocrinus,  158. 
Trimerella,  267,  269. 
Tripodisciuin,  41. 
Trochammina,  30. 
Trochus,  225. 
Tropidoleptus,  281. 
Tryblidium,  214,  215. 
Tuba,  84. 
Tubicinella,  333. 
Tubipora,  118,  119. 
Tubularia,  101. 


Turbinolia,  136. 
Turbo,  222. 
Turritella,  224. 
Turritopsis,  97,  100,  104. 
Tyroglyphus,  374,  375. 

Ultimus,  228. 
Unio,  209. 
Urocentrum,  22. 

Vanessa,  474. 
Velella,  109. 
Ventriculites,  75. 
Vemis,  212. 
Veretillum,  125. 
Vermetus,  224. 
Vermicularia,  224. 
Verongia,  86. 
Vespa,  481. 
Virgularia,  120. 
Vivipara,  231. 
Volvox,  60-62,  66. 
Vorticella,  23,  57-59,  61. 

Xenoneura,  396. 
Xiphigorgia,  125. 
Xiphosphoera,  41. 

Yungia,  319. 

Zaitha,  419,  421. 
Zaphrentis,  135. 
Zoanthus,  127. 
Zoothamnium,  59. 
Zoroaster,  164,  165. 
Zygospira,  284,  285. 


